Betrayal of an Endangered Species

Status and Management of the Southwestern willow flycatcher



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


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

Causes of past and continued population declines

Systemic and Stochastic Habitat Loss

Populations with few individuals at scattered sites are particularly sensitive to environmental catastrophes, which can result from both systematic pressures and stochastic perturbations (Thomas et al. 1990). Systemic pressures are ongoing and non-random forces that threaten habitat or individuals of a species and are usually human caused. For the flycatcher, these include livestock grazing, reduced flooding, inundation under reservoirs, land clearance, conversion to exotic species and brood parasitism (Tibbetts et al. 1994). These pressures continue to threaten the flycatcher rangewide, as evidenced by the high proportion of populations classified with a medium and high management threat.

Stochastic perturbations for the flycatcher include floods, fire, drought and windstorms. Flooding was, historically, essential for riparian habitat creation, but now because of the current small size and isolation of most flycatcher sites, short-term habitat losses from flooding can result in extirpation of individual flycatcher populations. Fire, historically, was rare in native riparian forests. With the spread of tamarisk, however, its occurrence likely has increased (see below). Tamarisk related fires have resulted in destruction of occupied flycatcher habitat in at least three locations (PZ Ranch, Mittry Lake and Martinez Lake).

Systemic and stochastic habitat loss continue to threaten and eliminate flycatcher habitat and populations rangewide, the USFWS states:

"Additional habitat losses are likely to include both small- and large- scale losses and be of the same types that have occurred to date. The Southwestern willow flycatcher evolved in a system that was highly dynamic and best characterized as one where local losses of "ephemeral" riparian habitat were buffered by a regional abundance of habitat and a scale of habitat continuity that is difficult to imagine in today's highly fragmented landscape. Renewal and regeneration was as much a part of that dynamic as was destruction and loss. In the last 100 years of development in the Southwestern United States, the overwhelming trend for riparian forests has been loss and conversion without renewal." (USFWS 1997b)

Cowbird brood parasitism

The Southwestern willow flycatcher is seriously threatened by brood parasitism from the brown-headed cowbird. Cowbirds lay their eggs in the nests of other species, leading to nest abandonments, poor nestling survival and overall lowered nest success rates. This can result in population declines and, if extensive, extirpation of individual populations (Harris 1991, Whitfield 1990, Whitfield and Strong 1995). For example, flycatchers at Kern River declined from 44 to 27 pairs between 1989 and 1993, partially because of brood parasitism that resulted in nest success rates as low as 18% (Whitfield 1993).

Cowbird presence has been positively documented at 100% of all remaining flycatcher sites (table 17). Of the 40 sites where nesting has occurred and been monitored, parasitism has been documented at 26 (65%) of these sites.

Causes of high cowbird parasitism rates. Habitat degradation and cowbird numbers are integrally related, as evidenced by the dramatic increase in the cowbird's range, corresponding to the onset of grazing, urbanization and agriculture in the past century (Rothstein et al 1977).

Land clearance increases foraging habitat for the cowbird, which feeds in agriculture fields, garbage dumps, cow pastures and other human dominated systems (e.g. Airola 1986). Habitat loss and fragmentation also decreases the ability of flycatchers and other birds to conceal their nests by increasing edge to interior ratios, allowing cowbirds to more effectively parasitize nests and reproduce (e.g., Airola 1986, Harris 1991, Mayfield 1977, USFWS 1997a, Verner and Ritter 1983, Whitfield 1995). For example, cowbirds were observed at Lake Mead, but no parasitism was ever documented, likely because of the large size of this habitat patch (Marshall personal communication 1997).

Grazing is particularly implicated in increasing cowbird numbers. Cattle even in small numbers increase food availability for cowbirds and make flycatchers and other birds more susceptible to parasitism by reducing shrub cover and fragmenting habitat (e.g., Airola 1986, Harris 1991, Mayfield 1977, USFWS 1997a, Verner and Ritter 1983, Whitfield 1995). The link between cattle grazing and cowbird parasitism is summarized by Sferra et al. 1997:

"Use of adjacent land by cattle also has been shown to provide feeding sources that increase and concentrate the number of cowbirds in the area, resulting in an increase in brood parasitism. Cowbirds may travel 6.5 mi (10.5 km) to feed and as much as 12.4 mi (20 km) to breed from their roost sites at Ft. Hood, Texas. Also, cowbirds may fly up to 4.3 mi (7 km) between feeding and breeding areas."

Table 17, cowbirds and flycatchers.

Sites with cowbirds Breeding sites with documented parasitism
100% 65%


In part because of the difficulty involved in documenting nest-predation, it is frequently overlooked as a source of poor nest success rates and a limiting factor to population growth. Yet, predation may be having a greater impact on flycatcher populations than brood parasitism.

Whitfield (1998), who has collected a detailed nine year record of flycatcher populations and reproduction at the South Fork of the Kern River, documented higher rates of nest predation than brood parasitism in every year, including those prior to extensive cowbird control. With the advent of five years of extensive cowbird control nest success and fledglings per nest increased dramatically, but this increase was found to be insufficient to increase populations at Kern. Whitfield speculates that predation is a major factor limiting population growth at the South Fork of the Kern River.

Indicating that predation is a rangewide problem, McCarthey et al. (1998) documented nest predation rates of 30% for all of Arizona, whereas brood-parasitism rates were only 8%.

Though predation and predators are a natural part of any ecosystem, anthropogenic habitat fragmentation likely increase the ability of predators to find and prey on nests by increasing edge to interior ratios (Small and Hunter 1988, Whitfield 1990). Given that flycatcher habitat is significantly reduced to isolated, small patches across the landscape, habitat fragmentation may be causing a significant increase in nest predation for the flycatcher.

At the South Fork of the Kern River, Whitfield (1990) initially found a direct correlation between distance to forest-edge and predation, indicating habitat fragmentation is having an effect on predation. After more years of study, though, no correlation was found (Whitfield personal communication 1998). Whitfield's study area, however, changed dramatically during the course of her work because of inundation of habitat behind Lake Isabella by rising reservoir levels. Predator numbers and behavior may have been affected by this habitat loss in later years of the study (i.e. edge effects may have become less important as predators were crowded into a shrinking amount of habitat). More research is needed to determine the effects of small patch size and increased edge on predation rates, impacting the flycatcher.

Research is also needed to identify flycatcher nest predators, which are largely unknown. Depending on what species are preying on flycatcher nests, anthropogenic habitat changes may be responsible for local increases in predator numbers.

Interestingly, Whitfield (1998) documented a correlation between predation and distance to water, showing that nests constructed over water are less likely to be preyed on. This correlates well with extensive data, indicating that the flycatcher selects for standing water when choosing a nest site (e.g. Sferra et al. 1997), and provides further indication that lack of perennial flow in many Southwest rivers, caused by extensive changes in hydrology primarily related to grazing, dams and groundwater pumping is impacting the flycatcher and other riparian dependent birds.


Cattle grazing likely is the greatest threat to flycatchers range wide. Hundreds of additional river-miles would support flycatcher habitat within 10 years but for direct and indirect degradation and/or elimination of riparian habitat through cattle grazing. Cattle eliminate riparian habitat directly by feeding on and trampling vegetation and, indirectly, by compacting soils, degrading streambanks, and altering watershed hydrology and channel morphology (Klebenow and Oakleaf 1984, Ohmart 1994, Reichenbacher 1984, Taylor and Littlefield 1986).

Cattle grazing is currently impacting the habitat of a large portion of the limited number of remaining flycatcher populations rangewide. Active grazing is occurring or has occurred in the recent past at 46% of all flycatcher sites (table 18). An additional 7% of sites are not directly grazed, but are impacted by increased cowbirds related to nearby grazing. Cattle have been removed from only 8% of all sites, mostly because of litigation.

Table 18, grazing and the flycatcher.

Sites with livestock grazing Sites with nearby grazing Sites where livestock have been removed Sites with no on-site grazing unknown
46% 13% 7% 34% 13%

Tamarisk Invasion

Though flycatchers nest in tamarisk, the spread and dominance of tamarisk throughout the Southwest corresponds with the decline of the flycatcher and other riparian dependent bird species (Hunter et al. 1987, Hunter et al. 1988 and Rosenberg et al. 1991). Tibitts et al. (1994) state that the flycatcher is "generally absent where the exotic salt cedar (tamarisk) has replaced native riparian vegetation". Tamarisk is thought to provide less thermal protection, less preferred insect fauna for feeding, and less cover from predation or parasitism (Hunter et al. 1987, Hunter et al. 1988, Tibitts et al. 1994, Carothers and Brown 1991, Sogge and Tibbits 1992, Sogge et al. 1993 and Muiznieks et al. 1994).

Perhaps the most serious threat from tamarisk results from increased likelihood of fire. Native riparian broadleaf species are not conducive to burning and, as a result, fire was likely uncommon in riparian areas (Agee 1983). Because of the capability of tamarisk foliage to carry fire, its occurrence has likely increased within riparian areas of the Southwest (Paxton et al. 1996). Three fires have been documented in riparian habitat occupied by flycatchers since 1994.

The most serious was a 1996 fire on the PZ Ranch, which pre-burn was one of the largest flycatcher populations in Arizona. The fire burned through tamarisk killing a gallery cottonwood stand and eliminating seven flycatcher territories (Paxton et al. 1996).

Tamarisk is able to colonize and dominate sites following loss of native vegetation caused by habitat alteration related to dams and other flood control activities, groundwater pumping, fire, grazing, agriculture and development (Kerpez and Smith 1987, Rosenberg et al. 1991, Sudbrock 1993). Current estimates place ground covered by tamarisk in the Southwest at 1 million acres (Johnson 1986).

Tamarisk currently is monotypic or dominates at 26% of all flycatcher sites and is present at an additional 30% of sites (table 19). Likely, thousands of river-miles that once supported flycatchers are no longer suitable because of the dominance of tamarisk.

Table 19, tamarisk and the flycatcher.

Sites where tamarisk dominates Sites where tamarisk is at least present Sites where there is no tamarisk
26% 30% 43%

Dams, flood control and groundwater pumping

The damming of southwest rivers for flood control, storage and hydro-electric power has had an immense impact on the flycatcher and riparian systems in general. Ohmart (1993) describes the impact of dams on birds as:

"Dams create a multitude of problems for riparian habitats and are essentially the death knell for two of the most valuable avian habitat components - cottonwoods and willows and vertical profile"

Both cottonwoods and willows require disturbed, moist soils produced by natural floods to regenerate, and, thus, construction of dams, by eliminating and/or changing the flood regime, has resulted in total loss of riparian forests on many rivers in the Southwest (e.g. Brady et al. 1985, Reichenbacher 1988). Besides altering flood regimes, dams increase salinity, toxic to many native species (Ohmart 1993); lower the water table and eliminate perennial flow, resulting in dessication and loss of native vegetation (Brown et al. 1981, Stromberg et al. 1994); increase dominance by invasive tamarisk (Sudbrock 1993, Horton 1964); and inundate habitat beneath reservoirs. A secondary impact of dams is the development of the floodplain by agriculture and urban-sprawl.

Currently 19% of all flycatcher sites are found below dams and, therefore, are at risk of eventually losing their habitat to lack of flooding. Another 24% of sites are found above dams on reservoirs, all of which could be flooded in a wet year.

Similar to dams, other flood-control activities, such as levee construction, channelization, and rip-rapping, impact flycatcher habitat by eliminating or changing the flood regime. At least 5% of all flycatcher sites have been impacted by flood-control projects, including the Cliff-Gila Valley, site of the largest flycatcher population, where the river-channel was recently rip-rapped by Army Corps.

Finally, groundwater pumping and water diversion convert perennial streams to ephemeral streams, decimating riparian vegetation. Even in areas where perennial flow is maintained, groundwater pumping and diversion can lower the water table below the rooting zone for riparian vegetation, devastating flycatcher habitat (e.g. Stromberg et al. 1995, Minckley and Clark 1984). Thousands of river-miles no longer support riparian forests because of lack of water. Currently, at least 16% of all flycatcher sites are threatened by diversion or groundwater pumping.

Table 20, altered rivers and the flycatcher.

Sites below dams Sites on Reservoirs Impacted by dams Recent flood control activities Groundwater pumping and/or diversion
19% 24% 43% 5% 16%


Case studies: the political realties of endangered species management

The data and analysis presented in the previous sections demonstrate the flycatcher is in immediate danger of extinction. Though the USFWS has repeatedly acknowledged this fact, they failed to take necessary action to protect the species. Why? The following two case studies describe the political pressure mounted on the USFWS to not make waves by disrupting economic activity, even if this means overruling the agency's own biologists, violating the ESA and putting the flycatcher at increasing risk of extinction.

Congressman and agribusiness crush the USFWS and 1,100 acres of flycatcher habitat at Lake Isabella.

Under the ESA, preparation of a biological opinion is strictly shielded from political intervention, indeed from involvement of any kind outside the USFWS and the consulting agency. This rule was clearly violated during consultation over destruction of habitat and illegal take of flycatchers by rising reservoir levels at Lake Isabella.

Flycatchers are found on the Kern River Preserve and the South Fork Wildlife Area at the inflow of the South Fork Kern River to Lake Isabella. The Kern population is the largest in California and one of only two populations rangewide that supports greater than 25 pairs with successful reproduction. As such, this population is absolutely critical to the long-term survival of the flycatcher in California and rangewide.

Though overfilling Lake Isabella conflicts with the primary purpose of the dam, flood-control, the Army Corps has consistently done so, in order to subsidize powerful agricultural interests thirsty for water. This practice, unfortunately, also floods habitat on the South Fork Wildlife Area. In 1995 flooding resulted in the illegal take of four nests by inundation. Though the USFWS notified the Army Corps that they were in violation of the ESA, the Corps continued to flood habitat through the 1995 breeding season.

When in 1996 the Army Corps again planned to flood habitat, the USFWS notified them of their need to consult over impact to the flycatcher. Fearing loss of control over management of the dam and resulting loss of water for agribusiness, Army Corps and the water lobby recruited and received help from Representative Calvin Dooley (D-CA) to subvert the consultation process. To stall for time, Army Corps only agree to consult on 1996 operations of the reservoir, although the USFWS requested consultation on long-term operations.

At the behest of powerful agricultural interests, who contributed $216,299 to his campaign, Representative Dooley wrote a letter to Katie McGintie head of President Clinton's Council on Environmental Quality, which oversees all Federal environmental agencies, threatening an election year "controversy" over the Endangered Species Act. In response, McGintie ordered John Garamandi, Assistant Secretary of Interior, to neutralize the situation by ordering the USFWS biologist handling the biological opinion to not call jeopardy and only consider alternatives that do not involve limits on reservoir size. It is clear from numerous documents the USFWS' biologist did not agree with these determinations. Garamandi, however, forcefully argued that "the Endangered Species Act is more endangered than the flycatcher". At the behest of Garamandi and company, the regional head of the USFWS went as far as to suggest that the biologist "haze" flycatchers at Lake Isabella, so they won't nest, removing take. In response, the biologist correctly pointed out that this itself would be take.

In direct violation of the ESA, Garamandi organized meetings between the USFWS, Dooley, Army Corps, and the Kern River Water Master and arranged for Dooley to review proposed mitigation measures, which he consistently vetoed. Then, prior to the release of the biological opinion, Garamandi and Dooley appeared together in a press conference announcing there is "no problem" at Lake Isabella and "business as usual" can continue. The USFWS biologist did as told, but documented in the biological opinion that political negotiation, not biology, guided the decision:

"Water management alternatives to avoid impacts to southwestern willow flycatchers were not addressed after January 29, 1996, when representatives of the Department of Interior, the Corps, and the Service made a public statement that such alternatives would not be considered for the 1996 water year with the understanding that the Service and the Corps would accept responsibility for any take of southwestern willow flycatchers"

"The status of the southwestern willow flycatcher is expected to decrease with time (p.9)...extirpation from California is possible, even likely" (P. 10)

For their 1996 operations, Army Corps only was required to protect 360 acres of habitat to mitigate loss of nine flycatcher pairs and up to 1,100 acres of native habitat. They eventually protected 95 acres, of which only a portion is riparian and all is grazed. Though failure to complete mitigation should have prevented Army Corps from continuing to flood habitat, the USFWS was too demoralized to even inform Army Corps of its latest ESA violation. When the Southwest Center sued Army Corps for not completing the mitigation, the USFWS amended the biological opinion to extend the completion time for mitigation.

Confident of their ability to keep USFWS in line, Army Corps entered into consultation over long-term operations. Again, jeopardy is not called, nor is lowering reservoir levels considered an option. Instead, Army Corps is required to protect the same 360 acres, which was required in the first consultation. A scientific team, however, is studying whether additional mitigation is required- we await the results. Following the Isabella fiasco, the USFWS biologist who authored the biological opinion voluntarily moved to a position, which did not involve endangered species issues.

Bureau of Reclamation calls the shots at Lake Mead

The Bureau of Reclamation manages Lake Mead and every other reservoir in its charge to maximize available water for agriculture and consumption. Endangered species concerns, even if legally mandated by the ESA, fall a distant second. At Lake Mead, this fact resulted in a tragedy for the southwestern willow flycatcher.

The inflow of the Colorado River to Lake Mead, prior to 1997, comprised one of the largest patches of native habitat in the Southwest with 1,185 acres of Gooding's willow. In 1996, a total of 10 territories with 8 pairs were documented, but based on available habitat biological consultants for the Bureau estimate there may have been up to 30 territories. An additional six pairs occurred on the Virgin River Delta to Lake Mead in 1997, bringing the total to as many as 36 territories with 14 documented pairs.

In the same year that flycatchers were first documented at Mead, the Bureau allowed reservoir levels to inundate and destroy habitat, resulting in documented take of three flycatcher nests. As a result, the Bureau entered into consultation with the USFWS over Lake Mead and operations of its other dams on the lower Colorado River.

From the beginning it was clear the Bureau intended to flood all habitat on Lake Mead, regardless of impact to the flycatcher. In opposition to this stance, the Arizona field office of the USFWS produced a draft biological opinion, which determined jeopardy and called for immediately lowering reservoir levels at Mead and not reducing overall habitat on the lower Colorado. An administrative directive sent out with the draft strongly justified these actions:

"The RPA actions for the Southwestern willow flycatcher are strong, due to the precarious nature of the species' status, and are at this time considered the absolute minimum necessary to alleviate jeopardy."

A copy of the draft was sent to the Bureau for comments and was soundly rejected. Rather than holding firm, the USFWS moved control of the biological opinion away from Arizona to the regional office in Albuquerque and completely changed the RPA. They no longer called for saving habitat at Mead. Instead, the Bureau was required to "protect" 1,400 acres of habitat within five years. Statements in the draft biological opinion, which the regional office failed to remove from the final, directly contradict a strategy of mitigating Mead by protecting habitat elsewhere:

"Additional habitat loss and forced emigration/population fragmentation is inconsistent with the need to ensure the survival and recovery of the Southwestern willow flycatcher" (P. 146)

"The proposed action constitutes the depressed distribution, numbers, and reproduction of the species in the action area, which is already beyond the jeopardy threshold, and significant levels of take are likely." (P. 155)

That the biologists believed the jeopardy threshold was crossed prior to destruction of Mead clearly indicates jeopardy can not be alleviated by protecting habitat in the future, particularly since habitat available for protection will likely be of lower quality, lacking contiguity and large patch size essential for recovery of the species. This is supported in the biological opinion, which states:

"Given that Lake Mead contains one of the largest and most significant native riparian tracts in the Southwest, there is a high probability that dispersing flycatchers would settle into smaller, more isolated, habitat patches." (P. 142)

Against the best scientific judgement of their own biologists, the regional office of the USFWS bent over backwards to allow the Bureau to continue to destroy habitat and take flycatchers unabated. As part of this complicity, the USFWS rushed the biological opinion to completion after the Southwest Center sued the Bureau for taking flycatchers without a permit. The opinion was issued April 30, 1997, prior to the breeding season and not allowing time for surveys on the Virgin River, where USFWS biologists warned of the possibility of flycatcher presence. Indeed, six pairs of flycatchers were found on the Virgin River Delta to Lake Mead in 1997. Several documents indicate both the USFWS and the Bureau knew of habitat on the Virgin and the possibility flycatchers occupied this habitat. Had the agency waited to release the biological opinion, as their own biologists advised, this new information would have likely changed the outcome. Instead, impacts to flycatchers by destruction of habitat on the Virgin was not considered in the biological opinion or development of the RPA. Thus, the Bureau violated the ESA by taking flycatchers and habitat on the Virgin River without a permit.

To date, the USFWS has not acted to enforce this violation. In the end, the Bureau was allowed to inundate and destroy all habitat on Lake Mead, satiating both agribusiness and unrestrained urban growth, leading the biologist who wrote the draft biological opinion to label the agency itself as an agent of extinction:

"the Southwestern willow flycatcher is being piecemealed to extinction; the service is turning a blind eye to the aggregate effects of its own consultation process. This internal denial is as insidious as cowbird parasitism" (Memo from Rob Marshall USFWS, 4/24/97)

This same biologist left the USFWS shortly after the Lake Mead debacle.