Reoccupancy of historic breeding sites by Richardson's Merlin in Wyoming.

Authors(s): S. Anderson and L. Ayers

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Publication Date: 0000-00-00

Type: Annual, Completed Project

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Abstract: The merlin (Falco columbarius) is a small falcon that inhabits the prairie and sagebrush steppe regions of Wyoming. The status of the Richardson's subspecies, which occurs in Wyoming, is unknown. In 1998-99, we surveyed the majority of known historic nest sites in Wyoming and found 18 unique sites occupied by merlins. In 1998 breeding attempts (active nests) were identified at 10 sites and lone adults (2 lone adults - sex unk., 2 lone males) were observed at 4 additional sites. Of these 10 sites, subsequent breeding attempts were noted at 9 sites in 1999. In 1999 we also found lone merlin (1 lone adult - sex unk., 2 lone males, 4 lone females) at 7 sites, three of which were the same sites as 1998. No merlins were located at any of 52 random survey sites. Historic site reoccupancy was 17.2% (10/58) for confirmed breeding attempts, and 31.0% (18/58) when all merlin sightings were included. We did not locate merlins on the Green River corridor, a historic "hot-spot" in Wyoming, but our survey effort in this region was limited. While merlin relative abundance could not be determined through objective means that would allow extrapolation to the entire state, we did determine that merlins are more abundant and persistent at historic sites than previously documented. Sites can remain occupied (or be reoccupied) over extended periods of time (up to 34 years in this study) indicating a potentially stable population in Wyoming.

Keywords: Green River, animal, bird, Aves, ornithology, merlin, Falco columbarius, falcon, Richardson's merlin , Falco columbarius richardsoni , population, nest, nesting, population, mortality, breeding