Why does the herring gull lay three eggs?

J. Graves*, A. Whiten, P. Henzi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)


Food supplements placed daily beside the nests of herring gulls, Larus argentatus, for the first 5 days after the first chick hatched produced improved weight gains over this initial period and higher fledging success, particularly in the third chick. The fledging success of the fed group appears to be due to increased weight gain and not to increased parental protection in the supplemented period. Since there is indirect evidence that food is available this suggests that the parents are putting less effort into foraging for their chicks than they are able to, and less than is in the interests of the third chick, in the first days after hatching. On a separate colony we found that having three chicks in the brood for more than 5 days resulted in lower weight gains for the second chick, but not the first. We suggest that fledging three chicks rather than one or two greatly increases the parents' reproductive effort, and consequently interpret the third egg as primarily insurance against the loss of the first or second.

Original languageEnglish
Pages (from-to)798-805
Number of pages8
JournalAnimal Behaviour
Issue number3
Publication statusPublished - Aug 1984


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