Reduced egg investment can conceal helper effects in cooperatively breeding birds

A. F. Russell, N. E. Langmore, A. Cockburn, L. B. Astheimer, R. M. Kilner

Research output: Contribution to journalArticlepeer-review

173 Citations (Scopus)


Cooperative breeding systems are characterized by nonbreeding helpers that assist breeders in offspring care. However, the benefits to offspring of being fed by parents and helpers in cooperatively breeding birds can be difficult to detect. We offer experimental evidence that helper effects can be obscured by an undocumented maternal tactic. In superb fairy-wrens (Malurus cyaneus), mothers breeding in the presence of helpers lay smaller eggs of lower nutritional content that produce lighter chicks, as compared with those laying eggs in the absence of helpers. Helpers compensate fully for such reductions in investment and allow mothers to benefit through increased survival to the next breeding season. We suggest that failure to consider maternal egg-investment strategies can lead to underestimation of the force of selection acting on helping in avian cooperative breeders.
Original languageEnglish
Pages (from-to)941-944
Number of pages4
Issue number5840
Publication statusPublished - 2007
Externally publishedYes


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