Date: April 18, 2017
Source: The City University of New York
If you are raised by other species, then how do you know who you are? Although heterospecific foster parents rear brood parasitic brown-headed cowbird chicks, juvenile cowbirds readily recognize and affiliate with other cowbirds. That's because they have a secret handshake or password. Specifically, the "password" hypothesis helps explain this paradox of species recognition: Social recognition processes in brood parasites are initiated by exposure to a password: in the case of cowbirds, a specific chatter call. A new study appearing in the Journal of Experimental Biology describes the neural basis for password-based species recognition in cowbirds.
Roughly 1% of bird species are obligate brood parasites. Female obligate brood parasites shirk parental care duties by laying their eggs in the nests of other females. This breeding strategy is extremely successful for the female parasite but raises questions, particularly with respect to species recognition. For instance, how does a juvenile bird that is not raised by familial members come to recognize its own species and avoid imprinting on the host species that cared for it from the day it hatched? One possibility is that young brood parasites use a password to identify conspecifics, and learning about species-specific signals occurs only after the password is used to find conspecifics.
Researchers have now demonstrated the neural basis for password-based species recognition in an obligate brood parasite. They showed that the auditory forebrain regions in cowbirds, which respond selectively to learned vocalizations, such as songs, also respond selectively to non-learned chatter. However, if the password is not used to locate other cowbirds, the young brood parasite will mis-imprint on its host species -- a process manifested in the brain by elevated gene induction in response to the host's song.