AUTHORS: Adrianna Yoder, University of Missouri St. Louis; Anastasia Rahlin, Illinois Natural History Survey – Prairie Research Institute; Jalene LaMontagne, University of Missouri St. Louis
ABSTRACT: Loss of habitat is contributing to avifauna decline, including Red-headed Woodpeckers (Melanerpes erythrocephalus) that were historically widespread across eastern-central North America. In northeastern Illinois, Red-headed Woodpeckers are facultative migrators, where some will overwinter while others migrate south. In the winter, Red-headed Woodpeckers switch their diet from insects to tree hard mast, like acorns. However, oak reproduction is spatiotemporally variable, and therefore, acorn quantity likely influences their ability to overwinter by altering food availability. Our objective was to compare Red-headed Woodpecker local habitat use and selection between summer breeding-only tree cavities and those used year-round. In summer 2023, we located Red-headed Woodpecker tree cavities and measured habitat characteristics at four scales: cavity, cavity-tree, surrounding habitat, and territory, which included performing acorn counts. In winter 2023-2024, we monitored the same cavities with camera traps to determine their winter presence. For year-round cavities, the key habitat characteristic of continued cavity use into the winter was high acorn quantity, particularly of the red oak group. This requirement for winter use contrasts with summer breeding cavity selection which typically relies on open canopy, and high decay and diameter of the cavity-tree. Our results suggest that at broad scales, acorn production could also explain regional differences seen in Red-headed Woodpecker distributions which we are currently investigating using eBird data and long-term acorn counts. Our research highlights the importance of oaks and understanding oak reproduction in creating habitats that can sustain Red-headed Woodpeckers year-round.
