Advanced breeding dates in relation to recent climate warming in a Mediterranean montane population of Blue Tits Cyanistes caeruleus |
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Authors: | Jaime Potti |
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Institution: | (1) Department of Evolutionary Ecology, Estaci?n Biol?gica de Do?ana, CSIC, Av. Am?rico Vespucio, 41092 Sevilla, Spain |
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Abstract: | Trends in the onset of breeding, clutch size and numbers of hatchlings and fledglings are examined for a Mediterranean montane
population of Blue Tits (Cyanistes caeruleus) subject to recent warming in springtime monitored during 20 years. Blue Tits advanced their breeding dates in relation to
mean air temperatures in April and, as a consequence, laid larger clutches. However, increases in the numbers of hatchlings
and fledged young over time were not statistically significant after accounting for variables of influence. The entire breeding
season seems to have been displaced towards earlier dates by adjusting breeding time to increased temperatures in prebreeding
time, to which Blue Tits have been more responsive than Pied Flycatchers (Ficedula hypoleuca) in the same area. The alternative hypothesis, that interference competition with Pied Flycatchers for nestboxes and caterpillars,
the main common food base of nestlings, has been the driving force behind the advancement of laying of the Blue Tit population,
was not supported. However, the significant advance of breeding dates in Blue Tits has not been sufficient to overcome the
precipitous decline in reproductive fitness with the advancement of the season. |
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Keywords: | |
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