A Regional and Continental Scale Analysis of Orientation and Nest Box Occupancy by American Kestrels

The American Kestrel (Falco sparverius), the world’s smallest falcon, breeds across North America. Kestrels readily uses nest boxes to lay their eggs in because they are secondary cavity nesters. This means that kestrels do not make the cavities that they nest in, but rather nest in cavities made by other species prior. Previous studies that have investigated the relationship between American Kestrel box occupancy and box entrance orientation in North America have had differing results. Professional and citizen scientists across the continent have installed thousands nest boxes for use by kestrels during the breeding season. Many have shared their data regarding nest box characteristics (e.g., location, nest box orientation, height, etc.) and occupancy with The Peregrine Fund’s American Kestrel Partnership (AKP). We analyzed AKP data to determine if there was an association between box occupancy by kestrels and box entrance orientation. Preliminary findings suggest that, at the continental scale, kestrels use boxes in proportion to their orientation for all orientations except the southeast. At the continental scale, American Kestrels occupied southeast facing boxes significantly less than expected based on their availability. The underlying driver of this pattern is unclear and deserves further investigation because kestrel populations are in decline