Individual optimization of clutch size in great tits

摘要: Individual birds within a population often lay clutches of very different sizes1,2, even though those laying the larger tend to produce more young which survive enter subsequent breeding (recruits)3. Two hypotheses have been proposed account for such differences in clutch size4. The individual optimization hypothesis proposes that parents size from they can maximize recruitment: adding or taking away their nests will result lowered recruitment5. trade-off assumes cost reproduction; rearing offspring leads having future survival fecundity6,7. When given experimentally enlarged broods rear should therefore show an increased mortality reduced fecundity. We tested predictions these two by manipulating brood great tits Parus major over nine years, and following performance parents. Parents differed ability recruit offspring, this being reflected laid. did best, terms number recruited, own size: removing not increase recruitment rates. These results strongly support hypothesis. There was no evidence raising suffered higher decreased fecundity compared with raised natural broods. are unable establish reproduction consequently supported.