A study of the vocal behavior of adult bald eagles during breeding and chick-rearing

Abstract

Previous efforts to characterize the spectral and temporal properties of calls contained in the vocal repertoires of adult bald and golden eagles, Haliaeetus leucocephalus and Aquila chrysaetos , respectively, led to the generation of a catalog of call types with distinguishing acoustic properties (McGee et al., 2019). Calls analyzed as part of that investigation represent vocal activity produced by captive, adult birds, some of which are long-standing residents of the Raptor Center at the University of Minnesota, as well as temporary residents undergoing rehabilitation from injury. Here, we compare the spectral and temporal properties of those calls with calls produced by free-ranging adult bald eagles recorded along with video during nest preparation, courtship, egg incubation and chick-rearing activities at nest sites monitored by the Raptor Resource Project. One goal of this project is to determine if the vocal repertoire of bald eagles studied in captivity is representative of that of free-ranging wild eagles. Another goal is to determine the extent to which spectrotemporal characteristics of calls recorded from captive and free-ranging birds overlap. Findings from this study will provide guidance in ongoing efforts to develop acoustic alerting signals designed to minimize the risk of eagle-wind turbine collisions.