A within-clutch trade-off between egg production and rearing in birds

摘要: Here we compare the chick-rearing capacity of common terns Sterna hirundo that were given an additional chick at hatching (incurring rearing costs but no production costs), egg start incubation and costs) made to lay laying, costs). The brood enlargements within natural range sizes (i.e. two increased three). Only those pairs a free reared significantly larger compared with unmanipulated controls. results show for first time within-clutch trade-off between producing extra young. Although there was effect on or hatchling size as result production, parents incurring full young subsequently showed reduced provisioning, growth survival. These cast doubts interpretation previous enlargement experiments providing empirical evidence observed clutch are often less than Lack size, such have failed include costs.