Great tits lay increasingly smaller clutches than selected for: a study of climate- and density-related changes in reproductive traits



: Ahola MP, Laaksonen T, Eeva T, Lehikoinen E

Publisher: WILEY-BLACKWELL PUBLISHING, INC

: 2009

: Journal of Animal Ecology

: JOURNAL OF ANIMAL ECOLOGY

: J ANIM ECOL

: 78

: 6

: 1298

: 1306

: 9

: 0021-8790

DOI: https://doi.org/10.1111/j.1365-2656.2009.01596.x(external)


5. We suggest that increasingly favourable conditions in winters have enhanced the survival and resulted in the observed increase in great tit breeding density. This may have most concerned young and otherwise low-quality individuals, which also most likely end up breeding in the increasingly occupied low-quality territories. This hypothesis was indicatively supported by increased within-year variation in both laying date and clutch size. The changes could also explain the lack of advancement in laying date as well as the increasing selection for large clutch sizes as the fittest individuals most likely occupy the best territories and lay largest clutches.



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