Post-fledging care, multiple breeding and the costs of reproduction in the great tit

In species that initiate multiple broods in a single season there is usually a trade-off between the number of young in the first brood, and the timing and occurrence of subsequent broods in the same season. The hypothesis that experimental reduction of clutch size reduces the duration of post-hedging care was tested in great tits, Parus major, and the effect of second clutches on post-fledging care was also investigated. Parental care continued for 20 days (range 10-32 days) after fledging. Investment in successive clutches overlapped, and the duration of post-hedging care was positively correlated with the inter-clutch interval. Second clutches reduced the female's contribution to post-fledging care. The clutch size manipulation did not affect the duration of post-fledging care. It is concluded that factors other than the duration of post-hedging care mediate the effect of clutch size manipulations on second clutches, and an alternative hypothesis is discussed. (C) 1996 The Association for the Study of Animal Behaviour.