Do Red-cockaded Woodpecker (Dryobates borealis) cavity locations provide olfactory concealment from predators?

Abstract

Nest site selection is crucial for survival and fecundity of birds. Predators find nests using visual, aural, thermal, and olfactory cues, yet few studies have evaluated olfactory concealment of nests. Rat snakes (Pantherophis spp.) are common nest predators that use ground-level olfactory cues to detect nest locations. In Arkansas, USA, we evaluated if cavity locations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a species that experiences nest predation by rat snakes, were associated with airflow conditions known to provide olfactory concealment for other bird species. We used a 3-dimensional sonic anemometer to measure ground-level air velocity, turbulence, and turbulence intensity at cavity trees and unused trees, and at cavity and opposite orientations on trees. For all airflow variables, we found no differences between used and unused trees and orientations. Other factors such as landscape-scale vegetation cover, forest stand structure, and tree characteristics may be more important for providing visual concealment or optimal foraging conditions. However, it remains possible that such factors also convey olfactory concealment. For example, savannah-like forests preferred by RCWs may have greater air turbulence than closed forests. Further research on RCWs and other bird species to address additional aspects of olfactory concealment, and relationships between different dimensions of concealment (e.g., between visual and olfactory concealment), would give insight into how habitat management could provide multiple benefits to birds.