Geographic variation of the song of the Belding’s Yellowthroat Geothlypis beldingi in the Baja California Peninsula, Mexico

Acoustic communication is essential for exchanging information between individuals of the same species. In birds, song plays a vital role in mate attraction and territory defense, and when it varies between populations, it can create barriers to gene flow and promote speciation. The Belding’s Yellowthroat (Geothlypis beldingi) is an endemic bird of the Mexican state of Baja California Sur and is endangered because of declining populations. Its populations are small and highly fragmented, but knowledge of the effects of fragmentation on the ecology and behavior of this species, especially its songs, remains limited. Five allopatric populations along its distribution were studied to assess their acoustic geographic variation. Six acoustic variables from 31 individual songs were analyzed using two supervised classification and multivariate techniques. Our results revealed significant differences between the northern and southern populations, which are separated by approximately 350 km, but the relationship between geographic distance and song variation is limited and could be influenced by different factors. Our results suggest that population-level acoustic differentiation may be associated with the “archipelago-like” distribution of oases. This association with fragmentation should be corroborated by more phenotypic characters and genetic information to determine if there are two significant evolutionary units within this species or lineages at the species level.