Avian Conservation and Ecology (Jun 2019)
Timing matters: cloud cover and date influence probability of detecting nesting Chimney Swifts (Chaetura pelagica)
Abstract
One third of bird species in North America need immediate conservation action. Effective management and recovery actions for species of conservation concern require accurate methods of monitoring species occurrence that limit the incidence of nondetection error (when a species is falsely recorded as absent when it is present). The Chimney Swift (Chaetura pelagica) is experiencing widespread population declines in North America, possibly, in part, because chimneys used for nesting or roosting are being capped or demolished. In particular, the presence of nesting swifts in a chimney can be difficult to determine, and thus, it is important to design survey protocols that limit the incidence of nondetection error. Here, we used data from Bird Studies Canada's Citizen Science program, Ontario SwiftWatch, and dynamic occupancy models to examine factors influencing the probability of detecting Chimney Swifts at nest sites. We found that the probability of detecting Chimney Swifts at nest chimneys decreased with increasing cloud cover. We also found some support suggesting that detection increased moderately with date over the course of the nesting period (June-July). Based on our findings, we recommend that surveys aiming to identify Chimney Swift nest sites in southern Ontario, Canada should be conducted for at least one hour under clear skies, and as late in the nesting period as possible. The results of this study will inform survey design to reduce the incidence of false negatives during chimney surveys for nest occupancy, and as a result, help reduce Chimney Swift nesting habitat disturbance and loss.
