Gregarious roosting occurs among many species of raptors during winter, particularly among species of Accipitridae. Such behavior may convey benefits to individuals such as thermoregulation, improved foraging efficiency, and protection from predators (Beauchamp 1999 and references therein). Documenting communal roost sites and behavior at them is important for management and conservation and may be especially important for species of conservation concern because roost sites hold large numbers of individuals. Here, we document the first known winter observations of mass communal roosting and gregarious perching of American Kestrels (Falco sparverius). We observed these behaviors in the agricultural area of the Imperial Valley of southern California.
Falcons are known to roost together or in close proximity during migration, especially near and along barriers that cause birds to concentrate (Kerlinger 1989, Ferguson-Lees 2001, Fehérvári and Lázár 2014). Lesser Kestrels (Falco naumanni) roost communally during...