Habitat explained microgeographic variation in Little Penguin agonistic calls

Vocalizations in birds play a significant role in species and mate recognition as well as sexual selection. Geographic variation in vocalization is well studied in male songbirds but largely unexplored in seabirds and in females. We investigated variation in male and female agonistic and advertising calls between 4 populations of Little Penguins (Eudyptula minor) in South Australia. We also determined whether call similarity was better explained by the geographic distances between the colonies, by microhabitat variation, or by variation in the physical characteristics of the individuals. Further, we used playback experiments testing male and female responses to determine the biological importance of geographic call variation. Both agonistic and advertising calls differed between individuals and sexes, with males producing calls at higher frequencies than females. Our results also reveal significant variation in agonistic calls across the colonies, best explained by variation in microhabitat. However, resident birds did not discriminate between calls originating from different colonies. The behavioral patterns are discussed in relation to gene flow and population differentiation.