Red-bellied Woodpecker (Melanerpes carolinus) has increased in abundance at a western range margin

Patterns of species' distribution and abundance are dynamic in response to changes in land cover, climate, interspecific relationships, and other factors. There are many examples of latitudinal range expansions, contractions, and shifts associated with warming climate. Global change effects are also manifested along gradients of longitude, and woody plant encroachment westward into the Great Plains might also be creating opportunities for species to expand into new areas. We used data from the North American Breeding Bird Survey (BBS) to examine the abundance of Red-bellied Woodpecker (Melanerpes carolinus) at a western edge of its distribution in Texas, Oklahoma, and Kansas. We compared BBS data from 1968-1992 to data from 1993-2018, fitting a series of generalized linear models to best explain variability in abundance. The best performing model included an interaction between time period and longitude, indicating both a change in abundance and in the distribution of abundance over time. Specifically, we found that Red-bellied Woodpecker increased in abundance near its western distributional limit over the past 5 decades, beginning at approximately 94 degrees longitude.