Some effects of inclement weather conditions on the survival and condition of bull-headed shrike nestlings |
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Authors: | Masaoki Takagi |
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Affiliation: | (1) Laboratory of Ecosystem Management, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan;(2) Department of Biology, Faculty of Science, Osaka City University, Sumiyoshi, Osaka 558–8585, Japan |
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Abstract: | Inclement weather struck Japan in 1993, permitting a natural experiment for examining the effect of weather conditions on nesting success and nestling growth of the bull-headed shrike, Lanius bucephalus. Aspects of the breeding biology of bull-headed shrikes in relation to weather conditions and timing of breeding in 1992 and 1993 were examined. The two breeding seasons were divided into two periods, early and late, in each year. While the probability of nest survival in nestling stages during both periods was almost equal, the probability of nest survival in the egg stage during the early period was significantly lower than that during the late period. In 1993, the probability of nestling survival during the late period was significantly lower than during the early period; the late period had larger fluctuations of precipitation and was colder than the same period in 1992. The number of disappeared nestlings positively correlated with mean precipitation per day. The greater part of the disappeared nestlings was the lightest in each brood. Late breeders fledged lighter young than the early breeders. Although shrikes adopted hatching asynchrony, the late breeders could not surmount the unpredictable inclement weather in 1993. |
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Keywords: | inclement weather Lanius bucephalus Mayfield exposure day method nest success nestling growth precipitation |
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