Communication

The temperate zone model where males sing vigorously to defend seasonal territories and to attract social and extra-pair mates does not apply well to the many tropical birds that defend year-round territories. While tropical birds with seasonal territories often have high song rates that function in intersexual and intrasexual communication, year-round residents tend to have very low song rates presumably because their territory boundaries and neighbors are so well known. It is not well understood why some tropical species have a strong dawn chorus while others do not, or what role the dawn chorus versus daytime song plays in territory defense or mate assessment. Female song, and vigorous territory defense, is more common in tropical than temperate birds. Playback experiments to test the function of duetting in tropical birds have found much variation among species in whether territorial aggression is sex-specific and the extent to which the duetting pair cooperates in defense. Tropical birds also feature greater female plumage ornamentation, but relatively few studies have experimentally tested what role this plays in communication, mate choice, or territory defense.