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Western Yellow-billed Cuckoo surveys in Colorado
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The Yellow-billed Cuckoo is considered an imperiled species west of the continental
divide because of significant population declines during the 20th century. As a
result the Western Yellow-billed Cuckoo is a candidate species for listing under
the Endangered Species Act (Listing Priority 3). In Colorado, it is listed in the
Colorado Division of Wildlife’s Comprehensive Wildlife Conservation Strategy as
a Species in Greatest Need of Conservation (Tier 1). In western Colorado, in the
1950s and 1960s Yellow-billed Cuckoos were found breeding annually near Grand Junction
(Righter et al. 2004). Also, cuckoos were regularly detected as recently as the
early 1980s along the Uncompahgre and Gunnison Rivers near Delta (Rich Levad, pers.
comm.). However, during the Colorado Breeding Bird Atlas (1987-1994), breeding was
confirmed in only one location on the western slope, on the Yampa River in Routt
County (Colorado Bird Atlas Partnership 1998). Since then, only one potential breeding
location in the range of the Western Yellow-billed Cuckoo has been identified in
the San Luis Valley of south central Colorado (Banks and Lucero 2004). The discovery
of cuckoos in the San Luis Valley was also the result of RMBO surveys.
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Photo of Yellow-billed Cuckoo fledgling near Hotchkiss, Colorado on July 23rd, 2008
by Jason Beason
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In 2008, Rocky Mountain Bird Observatory (RMBO) received funding from three sources
(Bureau of Land Management, Colorado Division of Wildlife, and U.S. Fish and Wildlife
Service) to survey for Yellow-billed Cuckoos in western Colorado. The objective
of this project was to determine if Yellow-billed Cuckoos breed in the North Fork
of the Gunnison River (North Fork) valley in Delta County and measure the extent
of the population throughout western Colorado.
We conducted site occupancy surveys which involved using call-playback methodology
targeting Yellow-billed Cuckoos. During the call-playback surveys we played a recording
of a Yellow-billed Cuckoo call at each survey station in an effort to lure cuckoos
closer to the observer so that they could be seen and to encourage a vocal response
(following Halterman 1991). Surveys were conducted between the dates of 30 June
and 31 July.
RMBO surveys detected cuckoos at six locations in the North Fork valley and at three
other locations in western Colorado (Moffat and Montrose Counties). Also, during
the course of the effort, incidental sightings of cuckoos came from four locations
in the North Fork valley. Perhaps the most exciting result of the 2008 surveys was
finding a cuckoo nest with two nestlings in the North Fork valley near Hotchkiss
on 21 July. Prior to this summer, Yellow-billed Cuckoos had not been confirmed breeding
in western Colorado since 1998. These nestlings were seen after fledging from the
nest (photo). In all, we estimate the presence of twelve breeding pairs throughout
western Colorado in 2008.
For more information contact:
Jason Beason
Special Monitoring Projects Coordinator
jason.beason@rmbo.org or (970) 527-4625
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