Landscape and Microsite Characteristics of American Kestrel (Falco sparverius) Nest-Box Sites along Highway Corridors in Southeast Ohio

Abstract

Falco sparverius (American Kestrel), an obligate cavity-nesting bird species, has experienced declines in much of its range for decades. Among possible causes for the decline are loss of suitable habitat and availability of nesting cavities. The species seems to benefit from nest boxes installed at locations assumed to meet all other habitat requirements. Nest boxes mounted on billboard posts and the backs of road signs—especially along 4-lane highways—are becoming more commonplace because of the perceived cover associated with these landscapes. Based on monitoring American Kestrel occupancy of nest boxes (n = 37) from 2015 to 2017 in southeastern Ohio, we were able to create a database of occupied versus unoccupied sites, as well as documenting the presence/absence of Sturnus vulgaris (European Starling), an apparent competitor for nesting cavities. Using this database, we conducted a GIS-based analysis of land cover across multiple scales for each site, with the objective of identifying a suite of landscape-cover features that might enable deployment of nest boxes in the region with greater usage by American Kestrels. Using principal components analysis coupled with k-means clustering, we identified 2 landscape niche clusters, which differed significantly along the PC1 axis (P < 0.001). One cluster was occupied by American Kestrels and European Starlings, the other was occupied by European Starlings only. The American Kestrel-occupied cluster had 10–40% herbaceous and <15% cropland across all spatial scales, with a higher median percentage of forest being prevalent at the 3000-m scale. The European Starling-only cluster had more cropland and less forest cover. At the micro-scale, American Kestrels appeared to favor nest boxes located closer (median distance = 11.5 m) to the road surface than those placed further (median distance = 24.5 m) away. Future efforts should take these trends into account to effectively deploy nest boxes intended for American Kestrels and minimize availability to and possible occupancy by European Starlings.