“Do large song repertoires affect the ability to recognize
conspecifics by song?
Most territorial animals tend to be more
aggressive to strangers than to stable neighbors (a phenomenon known as the
dear-enemy effect). This behavior has been used to test the abilities to
recognize individuals by song in many songbirds with typically positive
results. In species with very large song repertoires, however, the dear-enemy
effect tends to be either weak or absent and this result has been interpreted
as a product of either (a) poor voice recognition abilities or (b) of a
perception of neighbors and strangers as similar threats. Distinguishing
between these two hypotheses has proven difficult and today there is still some
controversy about this topic. The tropical mockingbird (Mimus gilvus) is
a territorial species with very large song repertoires expected to show weak or
no dear enemy effect. In some parts of their range, these birds live in social
groups with two or more males that defend a common territory. We exposed focal
males to playback of strangers, neighbors (from shared and unshared
boundaries), comales (i.e. other males in the same social group) and own songs.
Our prediction was that given their joint territoriality, male mockingbirds
should show diminished responses to their comales relative to outsiders which
meant that recognition could be tested independently of the dear enemy effect.
As expected, tropical mockingbirds did not discriminate behaviorally between
neighbors and strangers but were clearly less aggressive to comales. Our
results indicate that these birds are capable of individual recognition and
suggest some insight into the mechanism involved. This manuscript is currently
under review in Animal Behavior. (Note: Jimena Riveros
was an undergrad at the Universidad de Los