Bias-corrected natal dispersal estimates fill information gaps for White-headed Woodpecker conservation

Abstract

Although the White-headed Woodpecker ( Dryobates albolarvatus ) has been used as a management indicator species to guide forest management in the western U.S., basic information on the dispersal behavior of this species is currently unavailable. However, understanding dispersal can provide key information for management and conservation by revealing the mechanisms by which species colonize new areas and restored habitat. To address this information gap, we tracked the dispersal of juvenile White-headed Woodpeckers from their natal areas to their first spring home range in 2014–2018 and estimated dispersal distances using an interval-censored bias correction method with field observations and aerial telemetry surveys. We also compared habitat features between dispersal locations and spring home ranges. The median bias-corrected dispersal distance was 22.2 km in the fall (95% confidence interval [CI] = 16.4, 29.1 km), with 90% of woodpeckers dispersing >4.8 km (95% CI = 2.7, 8.3 km). The following spring, the median bias-corrected natal dispersal distance was 24.6 km (95% CI = 17.9, 32.3 km), while 10 individuals with full detection histories dispersed a median of 7.7 km to their first breeding locations (range 1.2–23.0 km). Our natal dispersal estimates for juvenile White-headed Woodpeckers were longer than those for most other woodpecker species studied to date. In addition, we found that woodpeckers settled in mid-elevation areas with greater variation in canopy cover compared to dispersal locations. There was no difference in ponderosa pine ( Pinus ponderosa ) basal area between dispersal tracks and spring home ranges. White-headed Woodpeckers are a species of conservation concern due to habitat loss in western North America, and active management in Washington state seeks to restore overstocked ponderosa pine forests to pre-settlement tree densities which could benefit this woodpecker. Our results inform conservation and forest management efforts by suggesting that dispersing juveniles have the capacity to travel long distances to colonize restored forests.

Keywords

• dryobates albolarvatus
• movement
• pinus ponderosa
• ponderosa pine
• post-dispersal settlement
• telemetry