A dominant paradigm in ornithology is that passerines arrive on their breeding grounds, establish a territory, and remain on that territory for the majority of the breeding season. Our research on passerines in the mountains of the Great Basin, USA, challenges that paradigm. From 2001-2019, we conducted avian point-counts at 538 sites throughout the western and central Great Basin. At the same sites, we collected data on vegetation indices, microclimate, insect abundance, availability of fruit and seeds, snow melt timing, and primary productivity (measured as the normalized difference vegetation index).
Results/Conclusions
We used multinominal, single-species N-mixture models to examine elevational movements of 27 passerine species. Some species, including Lazuli Bunting and Black-throated Gray Warbler, moved upslope during their breeding seasons, whereas others, including Spotted Towhee and Fox Sparrow, appeared to move downslope. We tested relations between site variables and the abundances of species that moved elevationally during their breeding season. For example, primary productivity and fruit and seed availability had a significant and positive relation with abundance of Lazuli Buntings, suggesting their upslope movement is related to resource availability. Directional elevational movement during the breeding season may change understanding of reproductive ecology, effects of climate change on avian populations, and single-species occupancy and abundance modeling.