'Last word' effects of male advertising calls on female preference in little blue penguins

Playback experiments were conducted to investigate how advertising call overlap between male little blue penguins, Eudyptula minor, influenced other birds along shorelines in front of breeding colonies. We used a dual-speaker design in which calls from one speaker consistently overlapped those from the other speaker. Females approached overlapping advertising calls more than overlapped calls or a silent control speaker. At a proximate level, this might have occurred because 'masking effects' obscure information in overlapped calls that females require for mate choice. Alternatively, females may simply be able to locate overlapping calls (i.e. the last call they heard) more easily. Young birds and adult males did not distinguish between calling patterns. It is possible that call overlap is associated with dominance or other quality indicators; thus, females may approach overlappers more often because they represent higher quality mates.