Are chickadees good listeners? Antipredator responses to raptor vocalizations
Many animals gather information about predators with a variety of cues, such as visual, acoustic, and olfactory. Several species of birds, including chickadees, are good at discriminating between species of raptors using visual cues, and they can encode information about the threat level in their alarm calls. Much less is known about how birds discriminate between the calls of different species of predators. We played back the calls of three species of raptors to black-capped chickadees, Poecile atricapillus, mountain chickadees, Poecile gambeli, and chestnut-backed chickadees, Poecile rufescens, to determine whether they can discriminate between them using acoustic cues. We played the calls of two species of small, high-threat raptors, northern pygmy-owl, Glaucidium gnoma, and sharp-shinned hawk, Accipiter striatus, which have very different hunting strategies (mainly sit-and-wait ambush predator versus very fast surprise attack flights). We also played a larger, lower-threat northern goshawk, Accipiter gentilis. Black-capped and mountain chickadees responded much more to the calls of the two small, more dangerous raptors than to the northern goshawk; they also responded very differently to the calls of the two small raptors. Chestnut-backed chickadees did not respond differently to the calls of the three raptors. These results indicate that black-capped and mountain chickadees can make specific discriminations between the calls of these three raptors and that they encode information in their alarm calls in sophisticated ways.