Experimentally increased prebreeding male social behaviour has no effect on female breeding phenology and performance

- We studied effects of male song and behaviour on female breeding in starlings.
- There was high individual variation in natural song in prebreeding males.
- Manipulated male song elicited prebreeding behavioural responses from both sexes.
- There was no effect of treatment on females during the breeding period.
- Male prebreeding song did not appear to influence female breeding decisions/success.

In the context of breeding phenology, social behaviour (especially song) has long been considered an important 'supplemental cue' that females integrate with other environmental information to determine timing of egg laying. However, to our knowledge, no studies have experimentally manipulated song in the wild in the context of female breeding phenology and performance. We studied natural variation in, and response to experimental manipulation of, prebreeding song and social behaviour in European starlings, Sturnus vulgaris, to determine whether male behaviour acts as a phenological cue determining female timing of egg laying and subsequent, postlaying breeding performance. In our highly synchronous system, natural variation in prebreeding male song quality and singing effort was surprisingly high, and singing increased slightly closer to egg-laying date. There was a strong prebreeding response of both males and females to the playback treatment, but no effect on female breeding phenology (egg-laying date) or performance (nestbox occupancy, egg size, clutch size, total chicks hatched, total chicks fledged or double-brooding behaviour). Our 3-year study finds no evidence that male prebreeding song is a cue determining female breeding phenology or performance in starlings.