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

Executive Summary

This report compiles data on the status of and threats to all known populations of the Southwestern willow flycatcher up to 1997. Management threats, including dam operations, grazing, tamarisk invasion, cowbird parasitism, development and environmental stochasticity are described and categorized for each population, based on severity. Demographic vulnerability to extinction for each population is defined based on population numbers, reproduction and degree of geographic isolation. The management status of the flycatcher primarily by Federal agencies, such as the U.S. Fish and Wildlife Service (USFWS), is discussed in detail. The final section describes population status by river.

The Southwestern willow flycatcher (Empidonax trailii extimus), a riparian forest obligate, is one of America's most endangered songbirds, evidenced by four years (1994-1997) of nearly rangewide surveys. In 1997, approximately 550 territories, including 450 pairs, were located at 62 sites. Though this indicates a critically small population, the demographics of the flycatcher paint a worse picture. Nearly 80% of all documented sites comprise less than 5 pairs. Fourteen sites (19%) were extirpated between 1994 and 1997. Flycatcher populations are severely limited by lack of breeding and poor reproductive success. Of all territories, at least 18% consist of single males and less than a third of all sites successfully produced young in 1997. Flycatcher sites are widely scattered and geographically isolated. Approximately 75% of all sites are greater than 50 miles from the nearest breeding population within the same drainage. Because of small population size, poor reproduction and isolation, the majority of flycatcher sites (82%) are highly vulnerable to extirpation within at least the next five to ten years, resulting in magnified risk of extinction for the flycatcher rangewide. Indeed, the USFWS believes:

"Extinction of the Southwestern willow flycatcher is foreseeable. This low status rangewide, as well as in the action area, indicates a critical need to aggressively protect existing populations and to expand and enhance native riparian habitat and the suite of environmental conditions that promote such habitat."(USFWS 1997a)

Destruction of habitat is the primary cause of the flycatcher's perilous status. Cottonwood-willow riparian forests, at one time, formed a nearly continuous network on all major and minor river valleys throughout the Southwest. Johnson and Haight (1984) estimate that as little as 5% of the southwest's original lowland riparian habitat remains and is largely comprised of highly fragmented and isolated patches.

Livestock grazing, inundation of habitat by dams, groundwater pumping, lack of floods, exotic plant invasion, stochastic disturbances, brood-parasitism and predation are all serious threats for the flycatcher:

Despite the clear and precarious status of the flycatcher, two lawsuits were required to force the USFWS to list the flycatcher as endangered under the Endangered Species Act (ESA). They were similarly resistant to designating critical habitat. The Southwest Center for Biological diversity had to file and win two additional lawsuits before critical habitat was designated by order of the courts in 1997. The USFWS then designated critical habitat only including slightly over half the population, and just over half the river-miles recommended by its own biologist.

Since listing, the USFWS has consistently failed to take necessary action to protect the flycatcher, allowing every project that takes flycatchers and their habitat to proceed with little modification and, in several cases, inadequate mitigation. They have issued take permits for approximately 120 territories, nearly 20% of a subspecies the agency admits is going extinct.

The Southwestern willow flycatcher is only one of many species that are declining with loss of riparian habitat. Over 100 state and federally listed species in New Mexico and Arizona are riparian dependent (Johnson 1989). Of 161 bird species which nest in the Southwest's lowlands, a full 69% have suffered declines due to riparian habitat loss (Johnson et al. 1987).

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