Our Liiiiii^ Ri'.stmnt'.s — Binl.s 



91 



Fig. 4. Tlic luimhers of singing male soulhwestcrn wilKm 

 tlycalchers and flycatcher nests detected in the Grand 

 Canyon (river mi to 71). 1982-9.^. Dotted lines represent 

 years when surveys were not conducted. 



The lov\ bleeding population, historical 

 declines, and potentially limited piodLictivily in 

 the Grand Canyon retlect the plight of the 

 southwestern willow flycatcher throughout its 

 range. Declines have been noted virtually 

 everywhere the flycatcher occurs, and threats to 

 its survival are widespread and immediate. As 

 human activities such as urbanization, water 

 diversion, agriculture, and grazing in riparian 

 areas continue in the Southwest, so do the loss 

 and alteration of riparian habitat. Vital winter- 

 ing habitat in Mexico and Central America is 

 also being lost to similar human activities. 



Brood parasitism by brown-headed cowbirds 

 is another significant threat to southwestern wil- 

 low tlycatchers within the Grand Canyon and in 

 many other areas. In fact, cowbirds may be one 

 of the greatest threats in areas where breeding 

 habitat is protected, such as the Grand Canyon 

 and other national parks and protected areas. 

 Cowbirds lay their eggs in the nests of other 

 birds (the host), who subsequently abandon the 

 nests or raise the cowbird chicks. Female cow- 

 birds will sometimes remove or destroy host 

 eggs, and cowbird chicks often monopolize the 

 parental care of the hosts. Thus, cowbird para- 

 sitism can reduce the number of host young pro- 

 duced, and in some cases, cowbirds may be the 

 only young successfully raised by the host. 

 Such effects have been recorded for southwest- 

 em willow flycatchers in the Grand Canyon and 

 in other areas as well (Federal Register 1993). 

 Conversely, control and removal of cowbirds 

 have resulted in local increases in southwestern 

 willow flycatchers and other songbirds. 

 Cowbird brood parasitism is related to riparian 

 loss and fragmentation because cowbird para- 

 sitism is highest in fragmented habitats. 



The southwestern willow flycatcher is a 

 unique and valuable part of the riparian com- 

 munity in the Southwest. Although recent and 

 planned future surveys provide important status 

 and distributional information on the flycatcher 

 in the Grand Canyon and a few other areas with- 



in Arizona, there is a critical need for basic sur- 

 veys and ecological research (including the 

 effect of brown-headed cowbirds) on this 

 species throughout most of its range, particular- 

 ly in New Mexico, southern Utah, and 

 Colorado. As a riparian obligate species whose 

 continued existence is directly tied to the future 

 of our remaining riparian habitats, its precarious 

 status and historic decline help illustrate the 

 need for riparian preservation and management. 

 Such management is important not only for the 

 southwestern willow flycatcher, but also for all 

 plant and animal species that make up and 

 depend on these valuable riparian areas. 



References 



Broun, B.T 1988. Breeding ecology of a willow flycatcher 

 population in Grand Canyon. Arizona. Western Birds 

 I9(ll:25-.V^. 



Brown. B.T. 1991. Status of nesting willow flycatchers 

 along the Colorado River from Glen Canyon Dam to 

 Cardenas Creek, Arizona. U.S. Fish and Wildlife Service 

 Endangered Species Rep. 20. 34 pp. 



Federal Register. 1993. Proposal to list the southwestern 

 willow flycatcher as an endangered species, and to des- 

 ignate critical habitat. U.S. Fish and Wildlife Service 23 

 July 1993. Federal Register .'i8:39495-39522. 



Finch. D.M.. and RW. Stangel. 1993. Status and manage- 

 ment of Neotropical migratory birds; 1992 September 

 21-25; Estes Park. CO. Gen. Tech. Rep. RM-229. U.S. 

 Forest Service. Rocky Mountain Forest and Range 

 Experiment Station. Fon Collins. CO. 422 pp. 



Sogge. M.K.. T.J. Tibbitts. and S.J. Sferra. 1993. Status of 

 the southwestern willow flycatcher along the Colorado 

 River between Glen Canyon Dam and Lake Mead — 

 1993. Summary report. National Park Service 

 Cooperative Park Studies Unit. Northern Arizona 

 University. U.S. Fish and Wildlife Service, and Arizona 

 Game and Fish Depailment. 69 pp. 



Tibbitts. T.J.. M.K. Sogge. and S.J. Sferra. 1994. A survey 

 protocol for the southwestern willow flycatcher 

 iEiiipidoiutx Iraillii exrimus). National Park Service Tech. 

 Rep. NPS/NAUCPRS/NRTR-94/04. 24 pp. 



Southwestern flycatcher 

 {Empidoimx traillii extimus). 



For further information: 



Mark K, Sogge 



National Biological Service 



Colorado Plateau Research Station 



Northern Arizona University 



Box 5614 



Flagstaff. AZ 86011 



