We describe here an undocumented vocalization of male breeding Cooper's Hawks (Accipiter cooperii), including the ecological contexts in which this vocalization was observed. We also suggest a possible function of this call.
The call consists of a continuous series of short chirp notes that are readily distinguished from the other common calls of adult breeding Cooper's Hawks described by Meng (1951) and Rosenfield et al. (1991a, 2020); the latter references, with sonagrams, characterized all breeding adult vocalizations into cak-cak-cak, kik, and whaa types. The chirp call is similar to the kik call, but the chirp call is audibly distinct and has a lower pitch with less volume than the kik call. Further, the chirp calls were uttered in a continuous series of notes; this is not generally the case with the kik call.
We documented this call on 12 occasions among three North American populations of...