Female song increases predation risk: why females sing less than males — ASN Events

Female song increases predation risk: why females sing less than males (#817)

Sonia Kleindorfer 1 , Christine Evans 1
  1. Flinders University, Bedford Park, SA, Australia

In general, the sexual selection paradigm has centred on choosy females and ornamented males. Given asymmetrical gamete investment, females (who per definition have high initial investment into large costly eggs) should prefer males (who per definition have smaller renewable sperm) that maintain costly ornaments. Song is a sexually selected trait and may be used by males to repel rivals and attract females. Little is known about the costs or functions of female song. Songbirds originated in Australasia and colonised the rest of the world, and it is likely that ancestral female songbirds sang. In extant species studied to date, female song occurs in 71% of species. Southern hemisphere songbirds generally do not migrate and many sedentary females and their pair males sing to defend the territory year-round. Southern hemisphere birds challenge classical assumptions about the evolution of sex differences in song. Given that song rate is under behavioural control, we test if song rate in female Superb Fairy-wrens (Malurus cyaneus) changes across the nesting cycle and if high song rate increases predation risk. Our observational data show changes in male and female song patterns across the nesting cycle. Both sexes had highest song rate during the fertile period, uniparental females lowered song rate during incubation, both sexes had lower song rate during the nestling period, and both sexes increased song rate to fledglings. In pairs where female song rate was high, predation of eggs and chicks increased. Using artificial nests, nests with higher song rate had more predation. Our study provides observational and experimental evidence for behavioural changes in song rate that predict predation risk, and could explain why females that lay and incubate eggs sing less than males.