Betrayal of an Endangered Species

Status and Management of the Southwestern willow flycatcher

 

SOUTHWEST CENTER FOR BIOLOGICAL DIVERSITY

Prepared by Noah Greenwald

Endangered Species Series No. 40

May 26, 1998


Table of Contents

I. Rangewide population status

II. Current management status

III. Causes of past and continued population declines

IV. Recommendations

V. Case Studies: the political realities of endangered species management

Agribusiness crushes the USFWS and the flycatcher at Lake Isabella
Bureau of Reclamation calls the shots at Lake Mead

VI. Status of the Southwestern willow flycatcher by river

The Colorado River
The Bill Williams River
The San Pedro River
The Gila River
The San Francisco River
The Little Colorado River
The Salt River
Tonto Creek
The Verde River
The San Luis Rey River
The South Fork of Kern River
The Santa Margarita River
The Santa Ana River
Mill Creek
The Mojave River
The Santa Ynez River
The Rio Grande
Coyote Creek
The Rio Chama
The Zuni River
The Virgin River

Bibliography

Appendix A: Biological opinions

List of Tables

Table 1. flycatcher populations are critically small
Table 2. the majority of flycatcher populations are isolated
Table 3. breeding status of the flycatcher
Table 4. demographic vulnerability classes
Table 5. demographic vulnerability of the flycatcher
Table 6. flycatcher population trends
Table 7. management threats
Table 8. assessing total management threats
Table 9. extirpated populations
Table 10. site names
Table 11. USFWS authorized take of flycatchers
Table 12. unequal mitigation
Table 13. Jeopardy decisions
Table 14. Contemporaneous non-jeopardy decisions
Table 15. Federal Agencies resist consultation
Table 16. Critical Habitat under three proposals
Table 17. Cowbirds and flycatchers
Table 18. Grazing and the flycatcher
Table 19. Tamarisk and the flycatcher
Table 20. Altered rivers and the flycatcher
Table 21. Colorado River Territories
Table 22. Bill Williams River Territories
Table 23. San Pedro River Territories
Table 24. Gila River Territories
Table 25. San Francisco River Territories
Table 26. Little Colorado River Territories
Table 27. Salt River and Tonto Creek Territories
Table 28. Verde River Territories
Table 29. San Luis Rey River Territories
Table 30. South Fork of Kern River Territories
Table 31. Santa Margarita River Territories
Table 32. Santa Ana River Territories
Table 33. Mill Creek Territories
Table 34. Mojave River Territories
Table 35. Santa Ynez River Territories
Table 36. Rio Grande Territories
Table 37. Coyote Creek Territories
Table 38. Rio Chama Territories
Table 39. Zuni River Territories
Table 40. Virgin River Territories


Status of the Southwestern willow flycatcher by river

Colorado River

Beginning in northern Colorado, the Colorado River flows south through Utah, Arizona, Nevada, California and Mexico to the Gulf of California. Each state and also Mexico lays claim to a share of Colorado water. As a result, the river now only flows to the Gulf in rare wet-years.

Nine dams have been built on the Colorado River, making it the most regulated river in the Southwest and perhaps the world. The first, Laguna Dam, was built in 1909, flooding eight miles of expansive riparian forests upriver (Hunter 1984). Below the dam the channel was deepened, leaving the former floodplain above flood stage.

The other eight dams had similar or worse impacts on the river, resulting in almost the complete loss of native riparian vegetation. Hunter (1984) described the condition of the Colorado this way:

"The Colorado River now supports few unaltered stands of vegetation. Almost all stands of mesquite, cottonwoods, and willows have at least some tamarisk associated with them. The creation of reservoirs has engulfed many riparian stands. Where one now sees agricultural fields from terrace to terrace extensive riparian forests once stood."

Tamarisk invasion, lack of flooding, dam operations, grazing, and agricultural development continue to degrade sparse remaining habitat.

As a result, the remaining flycatcher sites on the Colorado are fragmented into small population groups in isolated patches of habitat, which, because of degradation, are rapidly disappearing.

Nine sites supported flycatchers on the Colorado River until 1996. Five of these sites, all on the lower Colorado, consisting of single territories, declined to zero in 1997. Breeding has occurred only at 3 sites.

Colorado River inflow to Lake Mead.

Within the Lake Mead National Recreation Area, flycatchers occurred in what used to be an 1,100 acre patch of native willow habitat at the inflow of the Colorado to Lake Mead. This habitat was created during a series of dry years in the late 1980's, resulting in a decline in the elevation of Lake Mead. The USFWS characterized Lake Mead habitat as: "One of the largest and most significant native riparian tracts in the Southwest" (USFWS 1997a).

A total of ten territories with eight pairs were confirmed at Lake Mead in 1996 (Sferra et al. 1997), but based on available and un-surveyed habitat there may have been up to 33-40 territories (USFWS 1997a). If so, Lake Mead comprised greater than half the population on the entire Colorado.

Lake Mead flycatchers also were responsible for most of the successful breeding on the Colorado in 1996, fledging 10 of 12 total young with no occurrences of cowbird parasitism (Sferra et al.1997). Lack of parasitism is likely attributable to the large size of the habitat patch, enabling flycatchers to avoid edges where cowbirds are more common.

Despite the obvious importance of the Lake Mead Population to maintaining flycatcher populations on the Colorado, the Bureau of Reclamation, with Fish and Wildlife Service permission, began inundating habitat at Lake Mead in 1996, ultimately killing a large portion of the willows. This resulted in a documented decline in flycatcher territories and pairs (table 21). Three nesting attempts were made in 1997. At least one of these failed because of rising reservoir levels, which caused the nest tree to fall. One successful nest did produce four fledglings.

The USFWS has authorized destruction of all habitat at Lake Mead and extirpation of the entire population (USFWS 1997a).

While some birds may disperse to new habitat, this habitat is likely to be small, isolated patches of less suitable habitat, thereby causing flycatchers to decrease in survivorship and reproductive success. The biological opinion authorizing the destruction states:

"There is a high probability that dispersing flycatchers would settle into smaller, more isolated, habitat patches. Emigration to isolated habitat patches combined with the delay that dispersal entails, reduces the probability that flycatchers would obtain mates and breed successfully, and may reduce adult and juvenile survivorship."(USFWS 1997a)

Havasu National Wildlife Refuge.

Twelve pairs were found at Topock Marsh on the Havasu National Wildlife Refuge in 1997- a significant increase from past years.

Eight nesting attempts were made at Topock, fledging ten young. Cowbirds are plentiful on the refuge, resulting in one parasitized nest, which failed.

Habitat at Topock Marsh primarily consists of tamarisk with scattered overstory willows (Sferra et al. 1997). Because of increased likelihood of fire, presence of tamarisk threatens the long-term ability of this site to support flycatchers.

Several other sites have supported flycatchers on the refuge, but always in small numbers with little or no successful breeding. These sites also have substantial components of tamarisk.

Imperial National Wildlife Refuge.

Flycatchers were first documented on the Imperial National Wildlife Refuge in 1996, when six pairs were found between five locations (Sferra et al. 1997). No breeding occurred in 1996, perhaps because of numerous cowbirds. Only one pair that failed to breed, however, was found in 1997.

Tamarisk is pervasive throughout the refuge, including the flycatcher sites, and, as elsewhere severely increases risk of catastrophic fire. Lack of flooding, as a result of the dams, will only serve to increase dominance of tamarisk.

Cibola National Wildlife Refuge.

Two sites on the refuge each supported a pair of flycatchers in 1996 (Sferra et al. 1997). Walker Lake, which also had a territorial male, consists of a mix of native willow and tamarisk. The other site, near a landing strip, is dominated by tamarisk. No breeding occurred and cowbirds are numerous.

No flycatchers were detected at these sites in 1997 or anywhere else on the refuge. Lack of breeding and small numbers were likely factors in the extirpation of flycatchers on Cibola.

Grand Canyon National Park.

In the upper Grand Canyon, flycatchers have been documented at river-miles 50.5 to 51.4, 65.3 and 71. At river-mile 50.5-51.4 flycatchers declined from four pairs in 1994 to 1 pair with 1-2 additional territorial males from 1995-97' (Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). River mile 65.3 had a territorial male from 1994 to 95', but not 1996 (Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). River-mile 71 had two territories with one pair in 1993 that produced a nest with an unknown outcome (Muiznieks et al. 1994). In total, flycatchers in the upper canyon have declined by roughly five territories since 1993.

Nesting flycatchers at river mile 50.5 to 51.4 successfully produced one-two fledglings in both 1995 and 96'. Cowbird parasitism rates are high, however, 47% for all nesting between 1992 and 96'. As a result, flycatchers will likely not be able to sustain numbers without continued immigration.

In the lower Grand Canyon, flycatchers were documented at river-miles 267, 269 and near Bat Cave for the first time in 1997. A pair was documented at each of the three locations and at river-mile 269 nesting produced three fledglings.

Construction of Glen Canyon Dam and subsequent filling of Lake Powell have eliminated depositional floods in Grand Canyon, resulting in loss of beach habitat. To combat this problem, the Bureau of Reclamation intentionally flooded habitat in 1996. The USFWS consulted on this flood, predicting loss of up to two flycatcher territories from short-term habitat loss, and required the Bureau to limit flows to avoid flycatcher habitat.

Ehrenberg.

Consisting of two patches of habitat, one dominated by tamarisk and another mostly native, this area supported two territorial pairs in 1993 and a single pair in 1996 (Muiznieks et al. 1994, Sferra et al. 1997). One failed nesting attempt was made in 1996. Similar to several other sites on the lower Colorado, no birds were found in 1997 probably because of small numbers, poor habitat quality, and lack of breeding.

Mittry Lake.

Between Laguna and Imperial Dams, Mittry Lake occurs in a now dry section of the Colorado, only maintaining water because of a groundwater spring. This site, comprised of tamarisk, arrowweed and common reed, supported a single pair with no nesting in 1996 (Sferra et al. 1997). Zero flycatchers were found in 1997, which may be the result of a spring fire that destroyed the previously occupied tamarisk habitat.

Ferguson Lake.

This site, above Imperial Dam on the lower Colorado, has varied habitat and had one documented pair with no nesting in 1996 (Sferra et al. 1997). No flycatchers were found in 1997, again likely because of small numbers and lack of breeding.

Gadsen Pond.

A dry pond with a mix of willow and tamarisk near the town of Yuma, this site supported a single territorial male only in 1993 and 95' (Muiznieks et al. 1994, Spencer et al. 1996). Urbanization, lack of breeding and small numbers were likely all factors in the ephemeral nature of flycatcher use of Gadsen Pond.

Table 21. Status of the Southwestern willow flycatcher on the Colorado.



Site

Territories(pairs)

Nests/Young Fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Lake Mead NS NS 10(8) 6(6) NS NS 6/8 3/4 isolated medium D
Havasu NWR (multiple sites) 1 2 7(6) 12(12)(Topock Marsh) none none none 8/10 isolated high I
Imperial NWR (multiple sites) 0 0 6(6) 1(1) none none none none isolated high D
Cibola NWR NS 0 3(2) 0 NS none none none

EXTIRPATED

Grand Canyon 5(4) 4(1) 2(1) 4(2) 9/0 1/1-2 2/2 2/? isolated high D
Ehrenberg 0 NS 1(1) 0 none NS 1/0 none

EXTIRPATED

Mittry Lake 0 NS 2(1) 0 none NS none none EXTIRPATED
Ferguson Lake NS NS 1(1) 0 NS NS none none EXTIRPATED
Gadsen Pond 0 1 0 0 none none none none EXTIRPATED
Site Cowbirds Grazing Tamarisk Additional threats

Total management threat

Lake Mead present none none USFWS has permitted BOR to "take" entire population and habitat high
Havasu NWR (multiple sites) parasitism grazing some lack of flooding, salinization, fire medium
Imperial NWR (multiple sites) present grazing some lack of flooding, salinization, fire medium
Cibola NWR present grazing some lack of flooding, salinization, fire extirpated
Grand Canyon parasitism none dominates salinization, fire medium
Ehrenberg present none some lack of flooding, salinization, fire extirpated
Mittry Lake present none dominates lack of flooding, salinization, fire extirpated
Ferguson Lake present none some lack of flooding, salinization, fire extirpated
Gadsen Pond present none some urbanization, lack of flooding, salinization, fire extirpated

Bill Williams Drainage

The Bill Williams River is formed by the confluence of the Big Sandy and Santa Maria Rivers and flows from east to west into the Colorado in west central Arizona. Both Parker Dam (Lake Havasu on the Colorado River) and Alamo Dam flood portions of the Bill Williams. The primary purpose of Alamo Dam is to protect Parker Dam from flooding, but it was also traditionally managed for water use as well. Under a recent management plan, the U.S. Army Corps of Engineers has stated that, besides flood control, the purpose of the dam will now be to maintain wildlife habitat. Flood control, however, is still the primary purpose of the dam and during years of high water either Parker or Alamo Dam could flood occupied flycatcher sites and impact habitat.

Alamo Lake.

Near Southwest Brown's Crossing on Alamo Lake four flycatcher territories that produced two nests were documented in 1996 (Sferra et al. 1997). One of the nests produced two fledglings and the other had an unknown outcome. Flycatchers increased to five territories with four pairs in 1997, but only produced one nest with an unknown outcome in 1997 (McCarthey et al. 1998). Habitat is a large expanse of willow and tamarisk, which is grazed.

Lake Havasu.

Two sites on the Bill Williams Delta to Lake Havasu, within the Havasu National Wildlife Refuge, each supported one territory in 1996 (Sferra et al. 1997). Although one of the sites did have a pair, no nesting was documented. Likely because of lack of breeding, territories dropped to zero in 1997 (McCarthey et al. 1998). Habitat is high quality remnant gallery cottonwood forests with a mix of willow and tamarisk.

Lower Santa Maria River.

Found upriver from Alamo Lake on the Santa Maria River, this site supported one territory in 1994 and 95', rose to four territories with two pairs in 1996, and then declined back down to one territory in 1997 (Muiznieks et al. 1994, Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). Nesting has not been documented on the Santa Maria. Cowbirds are present. Habitat is a dense willow and tamarisk patch surrounding a beaver pond.

Highway 93 Bridge.

The highway 93 bridge had one territory in 1994, was not surveyed 1995-96, but probably maintained this territory, as it was again documented in 1997 ( Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). The habitat at the bridge, which consists of a dense overstory of cottonwood and willow with a willow and tamarisk understory, is at risk of further degradation from a planned bridge and highway expansion.

Lower Big Sandy.

At the inflow of the Big Sandy to Alamo Lake, flycatcher territories were documented in both 1994 and 1995, but not in 1996 (Muiznieks et al. 1994, Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). In 1995, it had six territories with two nests that produced two hatchlings and three eggs. The eggs are thought to have been depredated. Birds again returned to the lower Big Sandy in 1997 when four territories with one pair were found. The habitat is high quality willow and cottonwood with no tamarisk. Cowbirds are present.

Table 22, Status of the Southwestern willow flycatcher on the Bill Williams drainage.



Site

Territories

Nest attempts/young fledged

Population status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Bill Williams River Delta 1(1) 1 2(1) 0 none none none none

EXTIRPATED

Alamo Lake, Bill Williams NS NS 4(1) 5(4) NS NS 2/4 1/? isolated high I
Hwy. 93, Big Sandy River 1 NS 0 1 none NS none none isolated high S
Lower Big Sandy River 4 6 0 4(1) none 2/2? none none isolated high S
Lower Santa Maria River 1 1 4(2) 1(1) none none none none isolated high D
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Bill Williams River Delta present none some lack of flooding, desiccation, salinization extirpated
Alamo Lake, Bill Williams present grazing some inundation, fire medium
Hwy. 93, Big Sandy River present grazing some fire, bridge expansion high
Lower Big Sandy River present grazing some inundation, fire medium
Lower Santa Maria River present grazing some inundation, fire medium

San Pedro River

The San Pedro River flows from Mexico, above the town of Cananae, northward to the Gila River. It is the last major un-dammed river in the Southwest. In 1987, approximately 45 miles of the upper San Pedro were designated as the nation's first National Riparian Conservation Area (NRCA), prohibiting livestock grazing, mining, and off-road vehicle use. The NRCA is managed by the BLM. The lower San Pedro is predominately private property, including a Nature Conservancy holding.

Historically a beaver pond dominated, marshy ecosystem, the San Pedro is today a small, free flowing river, in places supporting extensive willow-cottonwood forests. Within the NRCA, are numerous abandoned gravel pits and agricultural lands slowly reverting to native riparian vegetation. Outside the NRCA, the lower San Pedro is a mix of riparian forests, farmlands, gravel pits, livestock grazing pastures, and homes. Interestingly, more flycatcher habitat currently exists outside the NRCA, reflecting the extent of damage to the riparian zone prior to its being protected in 1987. Recovery is evident within the NRCA, and presumably it will support more flycatchers and flycatcher habitat in the future...if the river is not completely or substantially desiccated by groundwater pumping.

The San Pedro does not flow perennially over its entire length, and no longer reaches the Gila River except when flooding. Surface flows are consistently present in gaining reaches where the subsurface geomorphology pushes water to the surface. In other stretches, the river is dry. Hydrologic studies from the upper river indicated that the water table is dropping due to excessive pumping of groundwater (Stromberg et al. 1995). Long-term well monitoring sites have documented a sinking water table and in the summer of 1997, the Charleston Narrows, well known as a gaining reach, nearly dried up.

Establishment of the NRCA did not confer federal water rights or limit groundwater pumping outside the NRCA. Recent expansion of the Army's Fort Huachuca and associated development in the Sierra Vista area has created a cone of depression in the aquifer, capturing water flow from the river itself and preventing groundwater from reaching the river. The cone intercepted the river in approximately 1990, and if not reversed is predicted to cause extensive dessication within two decades (McNish 1998).

On the lower San Pedro, where most flycatcher populations occur, groundwater pumping is primarily for mining, which draws substantial amounts of water. For example, the PZ Ranch, formally one of the largest flycatcher populations in Arizona, is a pumping site for ASARCOs Ray Mine. Groundwater pumping places the entire San Pedro watershed at risk of losing its native vegetation component to reduced perennial flow and a lowered water table.

LOWER RIVER POPULATIONS

Seven out of nine current and historical flycatcher sites occur on the lower San Pedro, outside the NRCA, near the confluence of the San Pedro and Gila Rivers. Most have remnant cottonwood-willow overstories with a component of tamarisk, which has increased the risk of catastrophic fire.

PZ Ranch.

The PZ Ranch is owned by ASARCO, a Canadian mining company and is used as a pumping site for its Ray Mine. Until recently, it supported the largest known flycatcher site in Arizona. In 1994, twenty one flycatcher territories were active, eighteen of which were occupied by breeding pairs (Sferra et al. 1995). Prior to a fire in 1996, there were 13 territories with 12 pairs. The fire raged through the tamarisk understory, burning two thirds of the occupied habitat and killing the cottonwood overstory, leaving only 6 territorial pairs (Paxton et al. 1996). Because tamarisk vigorously reseeds after fire, it will likely be the sole colonizer of the area, significantly degrading habitat suitability.

Cook's Lake Seep and Cienega.

The Cook's Lake area has supported significant numbers of mated and unmated flycatcher territories: 18 territories (7 pairs) in 1994, 16 territories (13 pairs) in 1995, 17 territories (15 pairs) in 1996 and 13 territories (13 pairs) in 1997 (Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996).

Successful nesting at Cook's Lake produced 16 fledglings in 1996. Nest failure was mainly caused by predation, rather than parasitism, resulting in 12 failed nest attempts compared to one failed nest attributed to cowbird predation (Sferra et al. 1997). Nine nesting attempts successfully produced 7 fledglings in 1997.

Tamarisk dominates at the seep, but is absent at the cienega. The area is privately owned and grazed.

Dudleyville Crossing.

This site was purchased by Bureau of Reclamation, as mitigation for destruction of habitat at Lake Roosevelt, and then turned over to the Nature Conservancy. A single pair nested and produced two fledglings in 1996 (Sferra et al. 1997). Three pairs were documented in 1997.

Cattle were removed from the site by the Nature Conservancy. Habitat is dominated by tamarisk with some willow and cottonwood.

Indian Hills.

Flycatchers were first documented at this site in 1994 when 5 pairs were found. Flycatchers declined to one pair in 1995, increased slightly to three pairs in 1996, and then increased dramatically to 15 pairs in 1997 (Sferra et al. 1997, Spencer et al. 1996). Likely, a large portion of this increase is due to movement of birds from PZ Ranch, following the fire, evidenced by the fact that of all sites surveyed in both 1996 and 97' on the Lower San Pedro, flycatchers increased by only three pairs. Twenty-Two nesting attempts successfully produced 17 fledglings. One nest was parasitized. Habitat is dominated by tamarisk. The site is privately owned and grazed.

CB Crossing SE.

Flycatchers were documented here for the first time in 1997, when five pairs were observed. Two nesting attempts produced one fledgling in 1997. Tamarisk dominates the site, cowbirds are present and it is grazed.

Wheatfields.

A single pair was documented at this tamarisk dominated site in 1997. The pair did not reproduce. The area is grazed.

UPPER RIVER POPULATIONS

Flycatchers have been found at three sites on the upper river within the National Riparian Conservation Area.

Soza Wash.

Soza Wash supported at least two unpaired flycatcher territories in 1993 (Muiznieks et al. 1994). Yearly surveys between 1994 and 1997, however, have not documented subsequent occupancy. The cause of this loss is unknown. Lack of nearby source populations makes recolinization at this time unlikely. Habitat is native willow and cottonwood.

Apache Powder Road.

Apache Powder Road had two territories (one pair) in 1996 (Sferra et al. 1997). A single nest failed due to cowbird parasitism. This site was not surveyed in 1997.

Highway 90 Bridge.

Highway 90 Bridge supported one pair in 1997, the first year of survey. Habitat is a mix of natives and tamarisk. Two nesting attempts with unknown outcome were documented.

Table 23. Status of the Southwestern willow flycatcher on the San Pedro River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
PZ Ranch 21(18) 16(14) 13(12) -6(6) 5(4) 11/2-15 11/11 15/4 6/9 connected high D
Cook's Lake Cienega 18(7) 9(7) 6(5) 7(7) 4/1-4 7/3 8/3 9/7 connected medium S
Cook's Lake Seep above 7(6) 11(10) 6(6) above 5/7 15/11 above connected medium S
Indian Hills 10(5) 3(1) 3(3) 15(15) 3/0-2+ 1/0 3/7 22/17 connected medium I
Dudleyville Crossing NS 0 1(1) 3(3) NS none 1/2 2/1 connected high I
CB Crossing SE NS NS NS 5(5) NS NS none 7/? connected high U
Wheatfields NS NS NS 2(1) NS NS NS none connected high U
Apache Powder Road NS NS 2(1) NS NS NS 1/0 ns isolated high U
Highway 90 Bridge NS NS NS 1(1) NS NS NS 2/? Isolated high U
Site Cowbirds Grazing Tamarisk Additional Threats

Total management threats

PZ Ranch parasitism grazing dominates groundwater pumping, loss of native vegetation by fire medium
Cook's Lake Cienega parasitism grazing none groundwater pumping medium
Cook's Lake Seep parasitism grazing dominates groundwater pumping, fire medium
Indian Hills parasitism grazing dominates groundwater pumping, fire medium
Dudleyville Crossing present removed dominates groundwater pumping, fire medium
CB Crossing SE present grazing dominates groundwater pumping medium
Wheatfields present grazing dominates groundwater pumping medium
Apache Powder Road parasitism grazing none groundwater pumping medium
Highway 90 Bridge present grazing some groundwater pumping medium

Gila River

The Gila River formally flowed from western New Mexico across Arizona to the Colorado near Yuma. Because of Coolidge and smaller diversion dams, and excessive groundwater pumping, much of the lower portion of the river no longer maintains perennial flow and, as a result, supports little riparian vegetation. Rea (1983) states:

"Only in exceptional places, such as about the junction of the Santa Cruz and Gila rivers, did surface flow continue until the 1950s. Groundwater levels dropped. As a result the entire riparian community of willows and cottonwoods was eliminated, being replaced along the river channel by exotic saltcedars."

Catastrophic habitat loss has resulted in the near extirpation of flycatchers from the Gila river below the town of Kearny near the juncture with the San Pedro River.

In contrast, upper portions of the Gila still support large populations of flycatchers. The absence of large cities or impoundments has resulted in the maintenance of perennial flow throughout most of the upper watershed in eastern Arizona and western New Mexico. Grazing and groundwater pumping for mining, however, are serious concerns on the upper Gila.

Cliff-Gila Valley

The largest known flycatcher population occurs in a 30 km section of the river near the town of Cliff, New Mexico (Skaggs 1996, Sferra et al 1997). In 1996, there was an estimated 135 territorial pairs, over 25% of the entire subspecies. The number of territorial pairs located increased to 174 pairs in 1997 (Leal personal communication 1997).

Breeding is believed to be extensive, but exact numbers are unknown because most nests are too high to be observed. However, Skaggs (1996) calculated a nest success rate of 50-55% based on 24 nest observations during 1995. He also calculated a brood parasitism rate of 16-27%.

Grazing does occur in the area, as it is owned by Phelps-Dodge Mining Company and the Forest Service, but is not extensive enough to have decimated habitat (Skaggs 1996). The primary purpose of the area is to maintain water rights for Phelps-Dodge's Tyrone Mine downstream.

In the 1970s, the Army Corps of Engineers built levees and rip-rapped much of the area for flood control and, as a result, lack of overbank flooding is a major cause of concern for the future of willow-cottonwood forests in the Cliff-Gila Valley. A flood did breach portions of the levee in 1993, however.

Gila Lower Box

This New Mexico site, managed by the BLM, has maintained around three territories since 1993 with some breeding (Muiznieks et al. 1994, Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996).

Cows were fenced from the area in 1995, resulting in a dramatic increase in native vegetation area and density (Murrehedge personal communication 1998). Cowbirds from nearby grazing, however, remain a concern. The USFWS authorized take of reproduction from two nests annually, resulting from brood-parasitism, and determined that this take constituted jeopardy (USFWS 1997c).

Safford Area

Several sites are found near the town of Safford, Arizona. The Sanchez Road crossing of the Gila supported four territorial pairs in 1996, up from two territories in 1995 (Sferra et al. 1997, Spencer et al. 1996). Six nests were found, but all failed because of parasitism and predation (Sferra et al. 1997). Declining to one pair in 1997, the Sanchez Road site produced one nest in 1997.

In 1995, construction of a new bridge destroyed 20% of the habitat at this site. The USFWS authorized take of two territories, which combined with high brood parasitism rates may result in elimination of this flycatcher population (USFWS 1995b).

Two other sites had birds in 1996: Solomon N.W. had three territorial males, and Smithville Canal had a singe territorial male (Sferra et al. 1997). Both of these sites declined to zero in 1997.

In 1997, two new sites were discovered near the town of Pima, where 14 territories (13 pairs) produced four nests. Breeding success was not monitored.

Along with native willows and cottonwoods, tamarisk is a stand component at all sites in the Safford area, resulting in increased risk of catastrophic fire.

The majority of this area is managed by the Safford District of the BLM and is heavily grazed. The district, which includes the Eastern Gila in Arizona and the San Pedro almost to the confluence with the Gila, has consulted with the USFWS over effects of its grazing program on the flycatcher and a number of other species.

As a result of this consultation, the BLM has promised to exclude cattle from occupied or unsurveyed suitable habitat during the breeding season, map potential cowbird foraging areas within five miles of occupied habitat and trap cowbirds if necessary. Because of these actions, the USFWS determined that grazing impacts did not constitute jeopardy, but did authorize an "indeterminable" amount of take, resulting from brood-parasitism.

Kearny Sewage Ponds

A tamarisk patch surrounding the town of Kearny's sewage treatment ponds had 6 territories with three pairs in 1996 (Sferra et al. 1997). Nesting at this site produced three fledglings in 1996. Flycatchers increased to eight territories and pairs in 1997 and produced 16 fledglings from 11 nests. Grazing occurs in the area and cowbirds are present.

Confluence with the San Pedro to Kelvin Bridge

Surveys in 1997 found 26 scattered territories and 22 pairs at ten sites on an 18 mile stretch of the Gila from the San Pedro to Kelvin Bridge, not including the Kearny Sewage Ponds. The largest of these sites had five pairs. Habitat is varied with patches of both native species and tamarisk. Ownership is mostly private. Surveys did not include nest monitoring.

Fortuna Wash

Near Yuma and the only site on the lower Gila, Fortuna Wash had one territory with no nesting in 1996 (Sferra et al. 1997). Similar to several nearby sites on the lower Colorado, this site declined to zero in 1997, likely because of small numbers and lack of breeding.

Table 24, Status of the Southwestern willow flycatcher on the Gila River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolated Vulnerability Trend
Cliff Gila Valley 98 135 134 174 NS NS NS NS isolated low I
Gila Lower Box 3 NS 3(3) 5(0) 2/0 NS 3/? none connected high D
Safford Area

(multiple sites)

NS 2 8(4) 16(14) NS 1/? 4/0 5/? isolated high U
Fort Thomas Bridge 1 NS NS 2/0 none NS NS none isolated high S
Kearny Sewage Ponds 1 NS 6(3) 8(8) none NS 4/3 11/16 connected medium I
San Pedro to Kelvin Bridge (multiple sites) NS NS NS 26(22) NS NS NS 11/? connected high U
Fortuna Wash NS NS 1 0 NS NS none none

EXTIRPATED

Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Cliff Gila Valley parasitism grazing none flood control, agriculture medium
Gila Lower Box parasitism removed none parasitism expected to result in take medium
Safford Area (multiple sites) parasitism grazing some agriculture, fire, new bridge destroyed 20% of site-habitat and 2 SWWF territories medium
Fort Thomas Bridge present grazing dominates fire medium
Kearny Sewage Ponds present grazing dominates fire medium
San Pedro to Kelvin Bridge (multiple sites) present grazing dominates most sites flood control, fire medium
Fortuna Wash present none some river channelization medium

San Francisco River

The San Francisco River runs east from Arizona into New Mexico, then south and west back into Arizona where it joins the Gila near the Arizona-New Mexico state line. The upper watershed is primarily National Forest Land, whereas the lower river is all private. Grazing is extensive on both Forest Service and private lands surrounding the San Francisco.

Alpine Horse Pasture.

This site, in the Apache-Sitgreaves National Forest, is the sole population on the San Francisco River, supporting four-five territories with three-five pairs annually since 1993, excluding 1997 when only two territories were found (Muiznieks et al. 1994, Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996).

Three nests produced seven fledglings in 1996 (Sferra et al. 1997). Although no brood parasitism was documented in 1996, one brown-headed cowbird young was documented in a nest in 1994 (Sferra et al. 1995). In 1997, one nest of three successfully produced three fledglings. At least one of the two nest failures resulted from predation (McCarthey et al. 1998).

Horse and elk grazing is the most serious threat to flycatcher habitat here, which consists of patches of geyers willow in a meadow. Flycatcher surveyors noted that shrubs in the pasture were "severely cropped" by ungulate grazing (Sferra et al. 1997).

As mitigation for grazing, the Forest Service is planning to control brown-headed cowbirds and construct elk proof fencing around suitable and potential habitat (USFS 1997). They, however, only plan to exclude horses from occupied habitat during the breeding season and not at all in unoccupied habitat. These actions fall short of recommendations, made by a team of flycatcher experts assembled by the Forest Service, to exclude both horse and elk year round from flycatcher habitat at Alpine.

Table 25, Status of the Southwestern willow flycatcher on the San Francisco River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Alpine "Horse Pasture" 5(5) 4(3) 4(3) 2(2) 5/2-6 3/4 3/7 3/3 isolated high D
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Alpine "Horse Pasture" parasitism horse none habitat degradation from continuing horse grazing non-breeding season

medium

Little Colorado River

The Little Colorado River cuts across Northwestern Arizona from the Apache-Sitgreaves National Forest to the Colorado River at Marble Canyon. The Little Colorado has one major dam at Lyman Lake and several minor dams. Reaches below Lyman Lake, surrounded by private, state and Native American lands, are severely impacted by grazing, and, as a result, support no flycatcher territories.

Greer.

This site is near the headwaters of the West Fork of The Little Colorado by the town of Greer at nearly 9,000 feet, making it the highest flycatcher site rangewide. The site has supported flycatchers at least since 1993. In 1996, Sferra et al. (1997) documented 11 territories with 10 pairs in two localities: four in town and seven on the River Reservoir. Territories and pairs declined by nearly half in 1997, likely because of failed reproduction in the previous year.

The Greer population produced ten nests in 1996, but all failed. Half of the nests were parasitized by cowbirds, three were lost because of weather, one was predated and one was deserted. The high rate of nest parasitism (50%) is likely the result of grazing on nearby allotments on the Apache-Sitgreaves National Forest and human presence in the Greer Area, and may be the reason why only six territories with five pairs were found here in 1997. The forest is not planning to reduce grazing on these allotments, but is going to institute a cowbird trapping program (USFS 1997).

The Greer area is within designated critical habitat, which includes the headwater areas of the West, East and South Forks of the Little Colorado.

Hall Creek and Nelson Reservoir.

Both sites supported a territory in 1994, but not in other years and, as a result are likely extirpated (Sferra et al. 1995).

Table 26, Status of the Southwestern willow flycatcher on the Little Colorado River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Hall Creek 1 0 0 0 none none none none EXTIRPATED
Nelson Reservoir 1 0 0 0 none none none none EXTIRPATED
Greer Town/River Reservoir 8(8) 9(7) 11(10) 6(5) 8/

3-11

7/12 10/0 3/5 isolated high D
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Hall Creek present grazing none   extirpated
Nelson Reservoir present grazing none Reservoir operations extirpated
Greer Town/River Reservoir parasitism grazing none Reservoir operations medium

Salt River

The Salt River flows across central Arizona to the Gila River west of Phoenix. The upper portion flows through the Fort Apache Indian Reservation. The middle and lower sections of the river flow through the Tonto National Forest and Phoenix, and are tightly regulated for urban and agricultural use by four dams. As a result, there is no longer perennial flow on the lower river.

The largest and only population of flycatchers is located on the inflow to Roosevelt Lake, the first of the Salt River reservoirs. Flycatchers were first documented here in 1993, when two territories were found. Since that time, numerous flycatcher territories have been documented: 25 territories (15 pairs) in 1994, 15 territories (9 pairs) in 1995, 22 territories (18 pairs) in 1996 and 18 territories (18 pairs) in 1997 ( Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996).

Ten pairs made 14 nesting attempts in 1996 with two nests successively producing four fledglings (Sferra et al. 1997). The others failed for a variety of reasons, including cowbird parasitism (3) and predation (6). Although the habitat mainly consists of dense tamarisk, the high nest failure rates are not inconsistent with other areas and the site has maintained a consistent breeding population with nine birds fledged in 1995 and four fledged in 1994. Nesting attempts and success increased dramatically in 1997 with 22 nests producing 25 fledglings. Only one nest was parasitized in 1997.

Despite the fact that this site combined with Tonto Creek (see below) supported more territories and produced more young than any other site in 1997 besides the Cliff Gila Valley, the Bureau of Reclamation, with U.S. Fish and Wildlife permission, has raised Roosevelt Dam to increase water storage for future development in Phoenix. Reservoir levels are not currently inundating the habitat, but will as soon as there is a high water year. This will result in the total loss of flycatchers on the Salt River.

In 1996, the USFWS determined that flooding this population will jeopardize the viability of the flycatcher (USFWS 1996a). Instead of deferring use of a full Roosevelt Lake, the Bureau of Reclamation was required to protect habitat elsewhere. They did this by purchasing habitat at Dudleyville Crossing on the lower San Pedro River, which is adjacent to PZ Ranch. Although this habitat is valuable because of it's close proximity to a number of large flycatcher populations, only three pairs were found in 1997, compared to 39 pairs on the Salt River and Tonto Creek.

The Salt River Inflow is currently being impacted by cattle grazing on the Tonto National Forest in the Poison Springs grazing allotment. Grazing is supposed to be limited to winter, but cattle were observed in the habitat during the 1996 breeding season by flycatcher surveyors (Sferra et al. 1997). According to the Forest Service, occupied habitat will be fenced in 1997 and unoccupied suitable habitat will be fenced in 1998. The Forest Service also plans to trap brown-headed cowbirds in the area. These actions are likely to improve the suitability of the habitat, but will be moot if inundation extirpates flycatchers from the Salt.

Tonto Creek

Tonto Creek, a tributary of the Salt River, flows into Roosevelt Lake and, like the Salt, supports large numbers of flycatcher territories that will be lost when lake levels rise behind the modified Roosevelt Dam. Surveys documented three territories in 1993, eight territories (seven pairs) in 1994, nine territories (eight pairs) in 1995, 17 territories (11 pairs) in 1996 and 21 territories (18 pairs) in 1997 all at the inflow to Roosevelt Lake (Sferra et al. 1995, Sferra et al. 1997, Spencer et al. 1996). A total of 16 birds were fledged from eight nests in 1996 with no documented cowbird parasitism, making Tonto Creek the most successful breeding site in Arizona in 1996. This success was repeated in 1997 with 25 nests, producing 34 fledglings. This is likely the result of a cowbird trapping program and exclusion of cattle by the Tonto National Forest. Successful breeding and habitat mitigation programs, however, are meaningless if the habitat is underwater.

Table 27, Status of the Southwestern willow flycatcher on the Salt River and Tonto Creek.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Salt River Inflow 25(15) 12(9) 22(18) 18(18) 10/

3-9

9/9+ 14/4 22/25 connected low I
Tonto Creek Inflow 8(7) 9(8) 17(11) 21(18) 7/1-8 8/14 12/16 25/34 connected low I
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Salt River Inflow parasitism removed dominates Impending destruction of habitat behind recently raised Roosevelt Dam, fire high
Tonto Creek Inflow parasitism removed dominates as above high

Verde River

The Verde River runs south through central Arizona to the Salt River and is primarily surrounded by National Forest Land. There formally were four flycatcher sites on the upper portion of the river: Tuzigoot Bridge, Tavasci Marsh, Camp Verde, and Ister Flat. The first two, which are adjacent, have since been extirpated.

Tuzigoot Bridge.

This site supported flycatchers at least since 1992, when four territories were observed. In successive years birds were consistently observed: two territories in 1993, three territories in 1994 and two territories plus one individual in 1995 (Sogge 1995). Breeding attempts occurred in 1993 (one cowbird fledged) and 1994 (two flycatchers fledged). Following bridge repair in December and January, 1995-96, no territories have been documented in either the 1996 or 1997 breeding seasons (Sferra et al. 1997).

Tavasci Marsh.

Likely because of habitat recovery following cessation of dairy farming, two territories were found at this site for the first time in 1996. Four nests were all abandoned, however, and no birds were found in 1997.

Reproduction at both Tuzigoot and Tavasci was not sufficient to sustain the population, likely because of human caused disturbance and brood parasitism. Disturbance includes a bridge with relatively high traffic volumes, a planned 900 unit housing development with golf course (Verde Valley Ranch) and nearby National Forest grazing, which increases cowbird numbers in the area. The relevant agencies have consulted with the USFWS on all these projects with the following outcomes:

The Verde Valley Ranch was predicted to extirpate the population, but instead it was lost before the project was built. As a result, it appears that mitigation efforts proposed in the Tuzigoot bridge and Windmill allotment biological opinions failed to maintain suitable habitat. The Verde Valley Ranch when built will likely degrade the habitat beyond repair.

Camp Verde.

With the loss of the Tuzigoot Bridge/Tavasci Marsh flycatchers, Camp Verde is the last substantial population on the Verde River. Flycatchers were first documented here in 1994 when seven territories with five pairs were found (Sferra et al. 1995). The area was not surveyed in 1995, but it was likely occupied because six territories with five pairs were found in 1996 (Sferra et al. 1997).

Birds are found in an isolated and exceedingly small linear patch of willows, cottonwood and tamarisk. Because of its size this habitat patch could easily be destroyed by flooding and because of its isolation flycatchers would have no nearby habitat to colonize (Marshall personal communication 1997).

Cowbird parasitism, likely relating to grazing on nearby National Forest lands, is a serious problems at Camp Verde. Of 13 nesting attempts, six (46%) were parasitized and failed, indicating that a trapping program is necessary to maintain this population. Despite the parasitism, nine flycatchers were fledged in 1996, which is likely why territories (10) and pairs (10) increased in 1997.

Ister Flat.

Farther down river, this site had one territory in 1993, and was not surveyed again until 1997, when it had two territories with one pair. The site is grazed. Cowbirds were observed in 1993, but not 1997. Habitat is dominated by tamarisk.

Table 28, Status of the Southwestern willow flycatcher on the Verde River.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Tuzigoot Bridge 3(2) 2(1) 0 0 1/2 NS none none EXTIRPATED
Tavasci Marsh 0 0 2(1) 0 none none 4/0 none EXTIRPATED
Camp Verde 7(5) NS 6(5) 10(10) 6/2? NS 13/9 19/22 isolated medium I
Ister Flat NS NS NS 2(1) NS NS NS none isolated high U
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Tuzigoot Bridge parasitism nearby some traffic, fire, 900 unit development extirpated
Tavasci Marsh parasitism nearby none traffic, 900 unit development extirpated
Camp Verde parasitism grazing some small patch size, fire or flood high
Ister Flat present grazing dominates small patch size, fire or flood med

San Luis Rey River

The San Luis Rey River flows west out of the Cleveland National Forest in San Diego County, California to the Pacific Ocean at Oceanside. A significant population of flycatchers occurs on 4.6 mile stretch of the river just below Henshaw Dam on National Forest, private and local irrigation district lands (Griffith and Griffith 1995, Haas personal communication). Unique to this site, the flycatchers build their nests primarily in coast live oak (Quercus agrifolia) - more than 70% exclusively in live oak, and a component of more than 79% of all nests. In 1997, Haas (personal communication) documented 36 territories with 33 pairs that fledged 49 young with not all habitat surveyed.

Native willow-cottonwood habitat was removed from portions of the San Luis Rey by the Army Corps in the 1950s, during an ill-conceived campaign to remove phearaphyte vegetation and conserve water. Henshaw Dam, which has effectively eradicated floods, may have limited recovery of some riparian vegetation, such as cottonwoods, along the river. Vegetation currently consists of large stands of mature coast live oak along the hillsides and upper benches of the river, and smaller stands of velvet ash (Fraxinus velutina) and scattered willow (Salix spp.) patches interspersed with large western sycamore trees (Platanus racemosa) on lower benches and closer to the river. The understory is varied and characterized by a mosaic of California rose (Rosa californica), California blackberry (Rubus ursinus), poison oak (Toxicodendron diversilobum), and creeping snowberry (Symphoricarpos mollis) (Haas personal communication). Extensive cattle grazing occurs upstream of the major flycatcher population (ibid.) In 1994, livestock were removed from the riparian area where flycatchers occur on National Forest lands. The Forest Service instituted a cowbird trapping program in 1992. The lower river has been severely impacted by urban development, agriculture, channelization and sand mining, all of which threaten the continued existence of flycatchers along the river within the coastal plain.

Table 29, Status of the Southwestern willow flycatcher on the San Luis Rey River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Upper San Luis Rey, River. 30(19) 29(27) 26(26) 36(330) 14/23 26/40 25/45 29/49 isolated medium S
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Upper San Luis Rey, River. Present nearby none lack of flooding, sand mining, groundwater pumping

medium

South Fork of the Kern River

The South Fork of the Kern River flows out of the Sierra Nevada Mountains and the Sequoia National Forest to the juncture with the mainstem of the Kern at Lake Isabella. Grazing, agriculture and/or development are all extensive throughout the watershed.

Significant numbers of flycatchers occupy native cottonwood/willow habitat at the inflow to Lake Isabella on the Kern River Preserve (National Audubon) and South Fork Wildlife Area (formally Army Corps, but now USFS). In 1996, 29 pairs fledged at least 58 young, making this the largest and most successful breeding population of flycatchers in California (Whitfield 1996).

An active cowbird trapping program dramatically increased the average number of young fledged from 24 to 41 per year and decreased parasitism rates from 63.5% to 14.4% between 1992 and 1996.

These gains, however, are negated by management of reservoir levels in Lake Isabella. Similar to both Lake Mead and Lake Roosevelt, the USFWS is allowing the Army Corps of Engineers to flood up to 1,100 acres of habitat, taking nine flycatcher territories. This is occurring primarily to procure more water storage for agriculture and development.

Rising lake levels have already had severe impacts in both 1995, when four nests were inundated, and in 1996, when flooding inundated former territories, resulting in a decrease from 34 (1993-1995) to 29 pairs (1996) (USFWS 1997b).

Fortunately, pair numbers have rebounded to 38 in 1997, but these gains may be offset by increased parasitism and predation in 1997, up to 29% for the former and 57% for the latter, possibly related to increased habitat fragmentation from flooding (Whitfield et al. 1998).

Table 30, Status of the Southwestern willow flycatcher on the South Fork of the Kern River.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
South Fork Kern River 34(34) 34(34) 29(29) 38(38) 32/42 32/40 29/58 51/37 isolated low I
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

South Fork Kern River Parasitism limited none Army Corps decision to destroy habitat behind Isabella Reservoir

high

Santa Margarita River

The Santa Margarita River, originating with the confluence of Temecula and Murrieta Creeks in the Temecula Valley, makes a short run from the Santa Margarita Mountains to the California coast at Oceanside. Unlike most California rivers the Santa Margarita primarily flows through federal land. The upper watershed is within the Cleveland National Forest and the lower watershed is within the Camp Pendleton Marine Corps Base. This provides a rare opportunity to manage the river for natural values with little conflict over private property. This, however, is not the current management plan.

The USFWS recently released a programmatic biological opinion on all Camp Pendleton base activities that impact endangered wetland and beach species, including the flycatcher. In this opinion, the USFWS authorized Camp Pendleton to take four flycatchers annually with little requirement to protect habitat. They are only required to maintain the same overall quantity of riparian habitat, regardless of importance to endangered species, such as the flycatcher. Essentially, they can destroy prime habitat, which is occupied by flycatchers, simply by promising to protect an equally sized area that may or may not currently support flycatchers.

Besides their routine training activities, which include troop movements, helicopter and other aircraft fly-overs, artillery fire and tank movements, the marines are planning several construction projects destructive to flycatcher habitat. The worst of these is a planned levee to protect a Marine Corps air station in the Santa Margarita floodplain. This project will eliminate a large flycatcher population, destroying occupied habitat directly and isolating additional habitat from essential flooding. Other construction projects include: a new bridge, sewage treatment plant pipelines, a diversion weir, and an airstation clear-zone. In total, the Corps predicts these projects will result in take of over 20 flycatchers, more than currently occur on the base.

Flycatchers have historically occurred on nine sites on Camp Pendleton. In 1997, the two largest sites were Los Flores Creek with seven territories and the Santa Margarita with 18 territories (seven Pairs). Other sites are limited to only one-two territories (Buck personal communication 1997).

The base does not conduct protocol flycatcher surveys and only notes flycatchers during surveys for least bell's vireo. This does not include searching for or monitoring flycatcher nests, resulting in a dearth of information to determine either flycatcher population trends or project impacts on flycatcher populations.

The base has been trapping cowbirds for several years to protect the least bell's vireo, which is assumed to be benefitting the flycatcher. Since the base does not monitor breeding, however, positive effects on the flycatcher are unknown.

Table 31, Status of the Southwestern willow flycatcher on the Santa Margarita River.



Site

Territories



Breeding

Population Status

1994 1995 1996 1997 Isolation Vulnerability Trend
The Santa Margarita River 9 10 13(4) 18(7) not monitored isolated high I
Los Flores Creek 3 2(1) 5(3) 7 " " isolated high I
De Luz Creek 0 1 0 0 " " EXTIRPATED
Horno Creek 0 0 1 0 " " EXTIRPATED
San Mateo Creek 0 0 0 1 " " isolated high U
Pilgrim Creek 4 4 2(1) 2 " " isolated high S
San Onofre Creek 7 1 0 0 " "

EXTIRPATED

Fallbrook Creek 0 1 0 1 " " isolated high S
Hidden Canyon 0 1 1 1 " " isolated high S
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

The Santa Margarita River present none none construction of a levee through occupied habitat high
Los Flores Creek present none none multiple threats from training related activities and construction projects medium
De Luz Creek present none none as above extirpated
Horno Creek present none none as above extirpated
San Mateo Creek present none none as above medium
Pilgrim Creek present none none as above medium
San Onofre Creek present none none as Above extirpated
Fallbrook Creek present none none as Above medium

Santa Ana River

The Santa Ana River flows west from the San Bernidino National Forest, through Los Angeles to the Pacific Ocean at Newport Bay. Prado Dam is currently the only impoundment. Between Prado and the ocean, the floodplain is heavily urbanized. Above Prado Dam, sand and gravel mining and water diversion are a major cause of habitat loss and degradation above the dam.

The sole flycatcher population on the Santa Ana is found in habitat surrounding Prado Lake. Territories have been documented here since the early eighties, but the area was not carefully surveyed until 1993, when 3 territories and one failed nest were found. Since then, there has been between 5-7 territories annually. In 1996, there were seven territories with four pairs that produced four fledglings (Pike et al. 1996). In 1997, five territories produced two nests and four fledglings (Hays personal communication 1997). Occupied habitat is a large stand of black willow with a mule-fat understory.

Because of the endangered least bell's vireo, cowbirds have been trapped in the basin for over 13 years. This has resulted in documented decreases in cowbird numbers and parasitism rates (Hays personal communication 1997).

Though no take of flycatchers was expected to occur, potential habitat has been lost behind Prado Dam because Army Corps at the request of Orange County modified the original purpose of the dam from flood control to water storage. This action did involve take of the least bell's vireo, however (Appendix A).

Plans are in the works to raise Prado Dam for still more storage. This will likely result in further habitat loss and potential take of flycatchers.

Of added concern, another dam is under construction upriver of Prado at Seven Oaks, resulting lack of floods and reduced water supplies may adversely effect critical habitat for the flycatcher, but no consultation has been conducted to date. As with Prado Dam, the proposed purpose of the Seven Oaks Dam was flood control, but once plans and construction were underway this was modified to also include water storage for bourgeoning population growth in Orange County.

Table 32, Status of the Southwestern willow flycatcher on the Santa Ana River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Prado Basin 5(2) 3(1) 7(4) 5(2) NS NS 5/4 3/5 isolated high S
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Prado Basin parasitism grazing none plan to raise Prado Dam for still more storage and a new dam upriver high

Mill Creek

Mill Creek, a tributary of the Santa Ana River in the San Bernidino National Forest, supported one pair with a nest in 1996 and two pairs with nests in 1997 that fledged five birds (Mckernan personal communication 1997).

Until recently, diversions for hydro-power and consumption dewatered Mill Creek, resulting in permanent loss of riparian habitat. In 1993, one of the diversions failed, allowing water to return to the creek and creating new habitat for flycatchers (Lowe personal communication). The habitat consists of white alder with a blackberry/willow understory.

Cowbirds were detected early in the season, but no parasitism was observed. There is no grazing within ca. Three miles of the site, but a nearby housing development and picnic area could provide feeding areas for cowbirds. The nearest large flycatcher population is on the Santa Ana River in the Prado Basin.

Table 33, Status of the Southwestern willow flycatcher on Mill Creek.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Mill Creek none none 1(1) 2(2) none none 1/3 2/5 connected high S
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Mill Creek present none none water diversion, housing development

medium

Mojave River

The Mojave River supports a small population of flycatchers upstream of Route 18 near the town of Victorville. In 1996, there were three territories, each of which produced a nest (Nuekirk personal communication 1997). Multiple cowbirds were observed in the area.

Surveys were conducted prior to a seismic retrofit on the Route 18 bridge, which ultimately removed habitat (Nuekirk personal communication 1997). Unfortunately, no surveys have been conducted in 1997 to determine if the construction had any impact or to see if birds returned to the site. Off-road vehicle use is reported to be a problem in the area (Nuekirk personal communication 1997).

Table 34, Status of the Southwestern willow flycatcher on the Mojave River



Site

Territories(pairs)

Nest attempts/young fledged 1996

Population Status

1994 1995 1996 1997 Isolation Vulnerability Trend
Mojave River, near Route 18 NS NS 3(3) NS

3/?

Isolated high U
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Mojave River, near Route 18 present nearby none off-road vehicles, loss of habitat for bridge repair high

Santa Ynez River

The Santa Ynez River flows out of the Santa Ynez Mountains, California to the coast near Lompac. Though the headwaters are in the Los Padres National Forest, most of the river is on private land. The Santa Ynez is regulated by three dams, which are upriver of current flycatcher populations.

The long-term viability of remnant habitat is likely jeopardized by lack of flooding caused by the dams. In addition, agricultural and urban development are increasingly encroaching on riparian areas in the Santa Ynez Valley. Despite this encroachment, the Santa Ynez was not included in critical habitat.

Flycatchers are found in a number of locations on a 25 mile section of the river, starting three miles upstream from the coast (San Diego Natural History Museum 1995). Flycatchers utilize stretches of the river that still have perennial flow and remnant willow-cottonwood forests (Holmgren personal communication 1997).

An estimated 17 territories with 29-31 individuals occur in scattered and small groups along the Santa Ynez. Neither annual surveys or nest monitoring are occurring on the Santa Ynez at this time, making it difficult to predict population trends.

There is no grazing within occupied riparian habitat, but nearby cattle and horse grazing on the Vandenberg Air-force Base and private lands, results in large numbers of cowbirds, which are being trapped.

Table 35, Status of the Southwestern willow flycatcher on the Santa Ynez River.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1995 1996 1997 Isolation Vulnerability Trend
Vandenberg Air Force Base to Buelton, CA 17(10-15) 17(10-15) 17(10-15) unknown isolated high U
Above Gibralter Reservoir 3 1-3 1-3 unknown isolated high U
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Vandenberg Air Force Base to Buelton, CA present nearby none agriculture, development, flood control medium
Above Gibralter Reservoir present nearby none agriculture, development, flood control medium

Rio Grande

The Rio Grande flows south from Colorado through New Mexico, then forms the border between Texas and Mexico, eventually flowing into the Gulf of Mexico. The Southwestern willow flycatcher only occurs in New Mexico and possibly southern Colorado.

There are three major dams and several minor diversion dams on the Rio Grande in New Mexico. This has lead to extensive agricultural development throughout much of the Rio Grande valley, particularly in southern New Mexico where much of the valley is privately owned.

In northern New Mexico and southern Colorado the Rio Grande is surrounded by mostly Forest Service and BLM lands and is heavily grazed.

The combination of agriculture, grazing and the dams has lead to the almost complete loss of native vegetation on the Rio Grande. Where riparian vegetation does exist, exotics, including both tamarisk and Russian olive, generally dominate. Despite these problems, the Rio Grande currently supports a number of flycatcher populations.

Alamosa National Wildlife Refuge and nearby McIntire Springs. In 1997, 27 flycatchers territories were documented on the upper Rio Grande in Colorado on the Alamosa National Wildlife Refuge and nearby McIntire Springs (Sogge et al. 1997). It is uncertain, however, whether these birds are Southwestern willow flycatchers or a different subspecies (Browning 1993) and, as a result, banding and genetic studies have been initiated (Sogge personal communication 1997). This study will ultimately determine whether other populations in Colorado are Southwestern willow flycatchers and whether these birds will receive protection under ESA.

Tierra Azul.

This site is a large beaver pond in the Carson National Forest with approximately 40 acres of dense willow habitat. Cattle are not actively excluded from the area, but much of the habitat is inaccessible because of interspersed channels of open water.

Three pairs were located in 1994, the area was not surveyed in 1995, and two pairs were found in 1996 (Maynard 1995, Cooper 1996 and 1997). Lack of successful breeding, likely, contributed to a decline to only a single territorial male in 1997 (Cooper personal communication 1998).

This site along with, Orilla Verde and Taos Junction Bridge are currently being impacted by BLM grazing allotments (USFWS 1997). The USFWS produced a biological opinion on these allotments, authorizing take of one pair from brood parasitism associated with grazing. This take was determined to constitute jeopardy for the flycatcher. The USFWS required the BLM to not graze cattle in areas occupied by flycatchers or unsurveyed potential habitat during the breeding season. They, however, did not require the BLM to trap cowbirds or restore habitat already degraded by grazing.

Taos Junction Bridge.

In 1996 a pair of flycatchers occupied a small patch of coyote willow on the Rio Grande between the Taos Junction Bridge and Pilar (Cooper 1997). One nest was found with eggs, which was later destroyed and presumed to have failed. Two territories with no nesting were documented in 1997.

The habitat is adjacent to a parking lot for boaters. Surrounding lands are managed by the BLM and heavily grazed.

Orilla Verde.

In 1994, a pair and a single male were found nesting at this site, which is a tamarisk dominated island on the Rio Grande (Maynard 1995). One egg and a nestling were observed in the nest. A pair was again found nesting on the island in 1996, but the nest was to high to document nest success (Cooper 1997). A second pair was found off the island on the adjacent bank, but were not observed to be nesting. Only a single pair was found in 1997, which produced one failed nest. This site is adjacent to a campground on BLM lands. Surrounding areas are heavily grazed and cowbirds have been observed in the vicinity.

Velarde.

Flycatchers were documented in the vicinity of the town of Velarde in both 1994 and 95', but no successful nesting was observed. In 1996, three sites each harbored a pair in the area, but all produced failed nests (Cooper 1997). Five territories with four pairs were found in 1997, when five nesting attempts produced two fledglings (Leal personal communication 1998). Cowbirds are numerous in the area, which is primarily private and used for agriculture.

San Juan Bridge.

This is the only site in northern New Mexico that has had more than 5 territories and successful breeding. In past years, two-three pairs were found in close proximity to the bridge, compared to five -seven pairs in 1996, when eight nests produced three fledglings (Maynard 1995, Cooper 1996 and 1997). Still more pairs were found in 1997, when 11 territories with ten pairs were located (Leal personal communication 1997). Habitat is dominated by Russian olive with patches of native willow and cottonwood.

A new bridge was constructed in 1995, which modified and altered ca. 3% of flycatcher habitat in the area. Following bridge construction, a fire burned much of the habitat in the vicinity of both the old and new bridges. Unfortunately, the 1996 surveys failed to document the impact of either the fire or the construction on flycatcher populations. Instead, surveys were expanded to include a 1.5 mile section upriver of the bridge without tracking the status of territories within the area of habitat disturbance.

Isleta Marsh.

This marsh on Isleta Pueblo lands, had four flycatcher territories in both 1995 and 1996 (Cooper 1996 and 1997). Breeding produced three fledglings in 1995, but only a cowbird was fledged in 1996. Informal surveys located three to four territories in 1997. Habitat is excellent with dense willow and a nearby gallery cottonwood stand. The long-term viability of this habitat, however, is compromised by flood control at Cochiti Dam.

Bosque Del Apache National Wildlife Refuge.

This refuge is an artificial wetland created with a series of dikes on the river. Despite large numbers of cowbirds, the refuge had four territories with one pair in 1996 that produced two fledglings from one nest (Cooper 1997). Two territories with one pair were documented in 1997 (Leal personal communication 1997).

San Marcial to Elephant Butte Reservoir.

A total of nine-eleven territories with two-three pairs were found between San Marcial and Elephant Butte Reservoir in 1996 (Cooper 1997). This is a decline from past years, when as many as seven pairs were found. Similarly, only one nest was found, which failed, compared to five-six in past years. This decline was likely caused by dewatering of the Rio Grande in 1996 by the controlling irrigation district. Only a single pair and several territories with single males were documented in 1997 (Leal personal communication 1998)

The Army Corps is evaluating impacts of a proposed channelization and levee project to increase water and sediment transport to Elephant Butte Reservoir that will include the entire stretch from San Marcial to the reservoir. This is likely to have serious impacts on flycatcher habitat, possibly desiccating riparian vegetation in the short run and likely cutting off riparian willow-cottonwood communities from regenerating floods.

Radium Springs.

Flycatchers were found on the lower Rio Grande in New Mexico for the first time in 1996 (Cooper 1997). One pair of flycatchers with 2 fledglings was detected in a linear patch of tamarisk and willow. The area is heavily developed for agriculture, but additional un-surveyed habitat was noted, indicating the possibility of more birds (Cooper 1997).

This site, along with several others that had been surveyed by New Mexico Game and Fish, was not surveyed in 1997. Despite the critical status of the flycatcher, Game and Fish does not consider annual surveys necessary (Williams personal communication 1997).

Table 36, Status of the Southwestern willow flycatcher on the Rio Grande.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Alamosa NWR & McIntire Creek NS NS NS 27 NS NS NS NS Possibly different subspecies
Tierra Azul 3(3) NS 2(2) 1(0) 3/? NS none none isolated high D
Orilla Verde 1(1) NS 3(3) 1(1) 1/1? NS 1-2/? 1/0 isolated high S
Velarde 1(1) 4(1) 5(3) 5(4) none none 3/0 5/2 isolated high I
San Juan Pueblo Bridge 4(3) 4(3) 13(7) 11(10) 2?/? 2/? 8/3 NS isolated high I

(survey effort)

Taos Junction Bridge NS NS 1(1) 2 NS NS 1/0 NS isolated high S
Isleta Marshes 3 4(2) 4(1) 3-4(0) unk. 2/3 1/0 NS isolated high S
Bosque del Apache NWR 3 2+ 4(1) 3(1) none none 1/2 NS isolated high S
San Marcial to Elephant Butte Reservoir. 11(7) 9(6) 14(3) 10(1) 5/? 6/2-3 1/0 2/2 isolated high D
Radium Springs NS NS 1(1) NS NS NS 1/2 NS isolated high U
Site Cowbirds Grazing Tamarisk Additional threats

Total management threats

Alamosa NWR & McIntire Creek present none   1996 fire destroyed some habitat

medium

Tierra Azul present nearby none   high
Orilla Verde present nearby dominates   high
Velarde present   dominates ditch realignment medium
San Juan Pueblo Bridge parasitism   R. olive dominates loss of habitat from construction and fire high
Taos Junction Bridge parasitism grazing some nearby parking area high
Isleta Marshes parasitism   some below Cochiti Dam medium
Bosque del Apache NWR present   some dewatering by Cochiti Dam and several diversion dikes medium
San Marcial to Elephant Butte Reservoir. Present   some dewatering, channelization projects for flood control high
Radium Springs present   dominates agriculture medium

Coyote Creek

Coyote Creek flows into the Mora river, which then flows into the Canadian River. This site is the sole flycatcher population on any drainage east of the Rio Grande in New Mexico, which includes the entirety of the rivers mentioned above, the Pecos River and several others. This range reduction is not uncharacteristic of a species heading towards extinction.

Two to three territories have been documented here annually since 1993, excluding 1995 when there was no survey (Maynard 1995, Cooper 1996 and 1997). This site was not surveyed in 1997. The birds are found in coyote willow in a beaver maintained marsh.

The area is a state park and, as a result, has some human impact, including cowbird presence. Breeding only occurred in 1993 when two pairs nested. Because of its isolation, small size and lack of breeding, this site has a high likelihood of extirpation in the near future.

Table 37, Status of the Southwestern willow flycatcher on Coyote Creek.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
State Park 2(2) NS 3 NS none NS none NS isolated high D
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
State Park present none none recreation and geographic isolation medium

Rio Chama

The Rio Chama flows south through northern New Mexico to the Rio Grande. The river is surrounded primarily by Forest Service and BLM lands and, as a result, is heavily grazed. Two impoundments impact the hydrology of the river and, in combination with grazing, have resulted in loss of native vegetation on most of the watershed.

Flycatchers are found in three scattered habitat patches near the town of Parkview. No successful reproduction has been documented on the Rio Chama in recent times. Grazing and cowbirds are present in the area. This site, like others that support small populations with little breeding, has a high likelihood of extirpation from systemic or stochastic processes.

Parkview/Chama.

In 1996, three-four territories and one pair were documented at this site, which is a slough adjacent to the Rio Chama surrounded by thick patches of coyote willow and alder with a cottonwood overstory (Cooper 1997). There were no surveys on the Rio Chama in 1997. The land is privately owned.

Los Ojos Fish Hatchery.

At this site two pairs of flycatchers were documented in 1994, none in 1995 and only a single territorial male in 1996 (Maynard 1995, Cooper 1996 and 1997). Habitat is characterized by native patches of coyote willow.

Burns Canyon Dam.

In 1994, one pair and one territorial male were found in what Maynard (1994) described as "the best flycatcher habitat in the area" because it was "the largest, had the best structure, and had ponded water".

In 1996 this habitat was not to be found and was presumed destroyed by flooding (Cooper 1996). As a result, only one territorial male was found in an exceedingly small patch that had recently been degraded by construction of a ditch.

Table 38, Status of the Southwestern willow flycatcher on the Rio Chama.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 Isolation Vulnerability Trend
Parkview/Chama none 1 4(1) NS none isolated high S
Los Ojos Fish Hatchery 2(2) none 1 NS none isolated high D
Burns Canyon Dam 2(1) 1(1) 1 NS none isolated high S
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Parkview/Chama present unknown none privately owned, agriculture medium
Los Ojos Fish Hatchery present grazing none   medium
Burns Canyon Dam present grazing none habitat lost to flood medium

Zuni River

The Zuni River Flows southwest from New Mexico into Arizona, where it meets the Little Colorado River. The upper watershed is within the Zuni Indian Reservation and is actively grazed. Two flycatcher sites occur on the reservation, both behind small reservoirs.

Flycatchers have been observed behind the dams annually since 1993, but have never had more than three territories at either site. Small numbers, little breeding and isolation results in a high risk of extirpation for flycatchers on the Zuni River

Black Rock Reservoir.

One pair with a nest of unknown outcome was documented in 1994. Since that time, only territorial males have been observed (Maynard 1995, Cooper 1996 and 1997).

Habitat consists mainly of native Gooding's willow. There is active grazing in the area, but apparently not to the extent that native vegetation is removed. Grazing has resulted in observed cowbirds, however.

Repair work on the Black Rock Dam temporarily drained the storage pond and channelized parts of the river. The BIA determined that this action would have no effect on the flycatcher and the USFWS agreed, despite the potential threat of habitat loss from both dewatering and construction equipment. Following construction in 1996 a fire destroyed a significant portion of the habitat, where past territories were documented. It is unknown whether impacts of the dam repair facilitated this event. A single flycatcher returned in 1997, but was found on the other side of the river than in past years.

Nutria Diversion Dam.

This site has had one pair with an additional one-two territorial males, consistently since 1993 and probably longer (Maynard 1995, Cooper 1996 and 1997). An adult with two young was observed in 1993, but no successful nesting was documented until 1997, when three pairs produced three nesting attempts and five fledglings (Albert personal communication 1998). Habitat is mostly native willow with scattered Russian olive. Both grazing and cowbirds have been observed here.

Table 39, Status of the Southwestern willow flycatcher on the Zuni River.



Site

Territories(pairs)

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Nutria Diversion Dam 2(1) 2(1) 3(1) 3(3) 1/0 none none 3/5 isolated high I
Black Rock Reservoir 2(1) 1 2 3(0) 1/? none none none isolated high S
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Nutria Diversion Dam parasitism grazing some R. olive   medium
Black Rock Reservoir present grazing none dewatering, dam repairs and a fire high

Virgin River

The Virgin River runs west across Utah into Arizona then Nevada, where it flows into the Colorado at Lake Mead. The hydrology of the river is severely altered by four dams, grazing, diversion, flood control and urbanization, and, as a result, harbors little native riparian vegetation.

Five sites support flycatchers on the Virgin River. The three largest occur in Nevada, collectively supporting 13 paired territories with successful nesting.

Virgin River Delta to Lake Mead.

The largest population of flycatchers on the Virgin occurs at the inflow to Lake Mead. Six pairs that produced seven fledglings were documented in 1997, the first year of surveys in this area (McKernan 1997). The site is dominated by native willows, despite active grazing.

As is the case with habitat at the Colorado inflow to Lake Mead, this habitat is slated to be destroyed by rising reservoir levels. No nests were flooded in 1997, but two were only three feet above lake level.

Unlike the Colorado, the Bureau of Reclamation does not currently have an incidental take permit to take flycatchers on the Virgin and is currently flooding the habitat in violation of the law. This is primarily because the USFWS rushed through a biological opinion before 1997 surveys were completed, despite prior knowledge that there was habitat likely to support flycatchers. They did this to avoid an impending injunction from a lawsuit filed by the Southwest Center that correctly argued the Bureau was violating section 9 of the ESA by destroying habitat and taking flycatchers. If lake levels continue to rise the Bureau will illegally take six pairs of flycatchers, which given the status of the flycatcher is significant.

Mesquite.

This site was first surveyed in 1996, when four pairs plus three additional territorial males were documented. Three pairs produced two fledglings in 1997 (McKernan 1997).

Livestock are grazed in the habitat and likely account for the documented cowbird parasitism. Habitat is dominated by tamarisk.

Flycatchers with crossbill mutations were observed at Mesquite in 1997. This is likely the result of agricultural pollutants, such as organo-chlorine pesticides. Birds with this mutations likely have lower survival rates because of difficulty in feeding.

Mormon Mesa.

Two territorial pairs were documented at this site in 1997 (McKernan 1997). Habitat is a mix of natives and tamarisk.

Muddy River Delta.

One territorial pair was found at this tamarisk dominated site in 1997 (McKernan 1997). The pair made two nesting attempts. This site will be flooded along with the Colorado and Virgin River deltas to Lake Mead.

Hurricane to St. George.

Four territories, including one pair, were documented in a 20 mile section of the river in Utah from below the Quail Creek Dam near Hurricane, to St. George. One nest was found in 1996, but it was not monitored throughout the season.

A total of 85 river miles on the Virgin in Utah were surveyed in 1996, including all areas surveyed in 1995 (McDonald et al. 1997). Areas were selected for survey based on available habitat, as determined by aerial photos. That four territories, including three single males, very likely comprises the total population on the Virgin in Utah is indicative of the degree of habitat degradation that has occurred.

Table 40, Status of the Southwestern willow flycatcher on the Virgin River.



Site

Territories

Nest attempts/young fledged

Population Status

1994 1995 1996 1997 1994 1995 1996 1997 Isolation Vulnerability Trend
Virgin River Delta NS NS NS 6(6) NS NS NS 4/7 connected high U
Mesquite NS NS 7(4) 3(3) NS NS NS 5/2 connected high S
Mormon Mesa NS NS NS 3(2) NS NS NS 3/4 connected high U
Muddy River Delta NS NS NS 1(1) NS NS NS 2/? Isolated high U
Hurricane to St. George NS 4(1) 4(1)   NS none 1/?   isolated high S
Site Cowbirds Grazing Tamarisk Additional threats Total management threats
Virgin River Delta Parasitism grazing none BOR destruction of habitat under Lake Mead high
Mesquite Parasitism grazing dominates Crossbill mutation high
Mormon Mesa present   some   medium
Muddy River Delta present   dominates BOR destruction of habitat under Lake Mead high
Hurricane to St. George present   some   medium