Effect of Social Environment on Acoustic Variables and Occurrence of Trumpet Calls of the Crested Auklet (Aethia cristatella Charadriiformes, Alcidae)

Abstract

Vocal plasticity under changes in social environment is well-known for passerine birds that possess vocal learning, but it has remained almost unstudied for other species. In this paper we studied the effect of social environment (the presence of conspecifics, a pair-mate, and a vocal duel), breeding period, and individuality on the acoustic variables and occurrence of self-advertising calls (trumpet calls) in male crested auklets (Aethia cristatella). This species is a planktivorous seabird that breeds in dense colonies and displays complex social behavior on the colony surface. We collected data in 2008–2010 and 2015 on Talan Island (Sea of Okhotsk); in total we used 1047 calls from 25 individually marked and 62 unmarked males. We found that the majority of males most often emit self-advertising calls when a pair-mate is absent, but other conspecifics are present; most rarely they emit self-advertising calls when a pair-mate is present, but other conspecifics are absent. However, there are some individual differences in those preferences. We suggest that, in the presence of a pair-mate, auklets prefer to use duet displays to signal their social status and pair-mate “occupation.” We also found that the effect of the social environment and breeding period on all acoustic variables measured is weaker than the effect of individuality. However, some of the trumpet call variables (mainly the duration of some syllables inside the trumpet call) changed significantly under the influence of the social environment and breeding period. Thus, crested auklets can slightly change the acoustic variables of their calls depending on the social environment, but keep the overall signature of their calls stable to make vocal individual recognition possible during the entire breeding season.