Abundance and occupancy of the western yellow-billed cuckoo (Coccyzus americanus) in Sonora, Mexico

Unveiling factors that determine abundance and distribution of endangered wildlife species has relevant implications in their conservation across international boundaries. For instance, the Western Distinct Population (as defined by the U.S. Fish and Wildlife Service) of the yellow-billed cuckoo Coccyzus americanus (Linnaeus, 1758) has disappeared in most of the species’ range across the western United States and southwestern Canada, but little is known about the conservation status at the southern edge of its breeding distribution in Mexico. To fill this information gap, we estimated abundance and occupancy rates of yellow-billed cuckoos using a standard broadcast call survey protocol. We used Bayesian spatial count models to estimate cuckoo population density at survey sites. We used Bayesian hierarchical models to estimate the effects of geography, climate, and vegetation on occupancy rates while accounting for imperfect detection. Mean cuckoo count per transect for all sites was C =..., We surveyed for cuckoos following the standard broadcast survey protocol for the species (Halterman et al. 2015) in the summers of 2015–2019 (5 years), but we reduced the number of surveys per sampling unit. We surveyed each site twice per year, with one survey occurring in each of the second and third standard survey periods. We reduced the number of visits per site to increase the number of sites surveyed. We conducted our first survey period from site from late June to late July and our second survey period from late July to no later than 16 August. For one upland site, we were denied access to conduct the second survey, and we instead surveyed the closest alternate upland site. We started the first survey period at the onset of the monsoon rains, which meant that at some sites, the rain effects of a greening vegetation were not always evident during the survey. 
At each site, we surveyed for cuckoos using point counts placed on transects along the riparian gallery forest or desert a..., Notepad ++ (available at https://notepad-plus-plus.org).