Ardea
Official journal of the Netherlands Ornithologists' Union

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Perrins C.M. & McCleery R.H. (2001) The effect of fledging mass on the lives of Great Tits Parus major. ARDEA 89 (1): 135-142
Studies of ringed Great Tits Parus major have shown that the mass of fledglings has a major impact on their futures. Heavier chicks are more likely to survive to breed and birds which are larger at fledging remain larger birds for the whole of their lives. The mass at fledging does not affect the breeding characteristics of males, but lighter females lay slightly earlier than heavier ones, while heavier ones lay slightly larger clutches. In years with low breeding numbers (when presumably there is low competition for territories) the new territory holders tend to have been heavy as fledglings, while in years with high breeding numbers (when presumably there is high competition for territories), more chicks of lower mass recruit into the breeding population. Hence, it does not look as if the number of new breeders is related, at least in any simple way, to the numbers of fledglings of high mass in the previous year


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