A. Aradis
G. Landucci
M.W. Miller
2003
<p><span>1. </span>Fat<span> </span>reserves<span> are stored energy that may help birds survive periods of harsh winter weather. This hypothesis predicts that </span>annual<span> </span>apparent<span> </span>survival<span> is higher for birds with large </span>fat<span> </span>reserves<span> than for birds with few or no </span>fat<span> </span>reserves<span> in winter. 2. </span>Blackbirds<span> (</span>Turdus<span> </span>merula<span> Linnaeus) were ringed in central Italy from 16 November to 20 February during 1990-2001. </span>Fat<span> scores were recorded for each bird. We used these capture-mark-recapture data for 1703 </span>blackbirds<span> to estimate the </span>effect<span> of large </span>fat<span> </span>reserves<span> on </span>annual<span> </span>apparent<span> </span>survival<span>, while controlling for transients, using computer programs SURVIV and MARK. Probability of birds retaining large </span>fat<span> </span>reserves<span>, or retaining few </span>fat<span> </span>reserves<span>, over 2 successive years was also estimated. 3. Birds with large </span>fat<span> </span>reserves<span> did not have higher estimated </span>annual<span> </span>apparent<span> </span>survival<span> than birds with few </span>fat<span> </span>reserves<span> (φ̂</span><sub>large</sub><span> = φ̂</span><sub>few</sub><span> = 0.595, SE = 0.043), inconsistent with our prediction. No </span>effects<span> of age, sex or year were detected on </span>annual<span> </span>apparent<span> </span>survival<span>. Birds with few </span>fat<span> </span>reserves<span> in any given year tended to have few </span>fat<span> </span>reserves<span> the following year (ψ̂</span><sub>few→large</sub><span> = 0.332, SE = 0.052). Birds with large </span>fat<span> </span>reserves<span> in any given year were unlikely to have large </span>fat<span> </span>reserves<span> the next year (ψ̂</span><sub>large→few</sub><span> = 0.585, SE = 0.080). 4. Large </span>fat<span> </span>reserves<span> may not increase </span>annual<span> </span>survival<span> of </span>blackbirds<span> wintering in central Italy. Winter weather in our study area may be too mild to </span>effect<span> </span>survival<span>. Alternatively, increased predation risk associated with large </span>fat<span> </span>reserves<span> may counteract any benefits of reduced starvation risk.</span></p>
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10.1046/j.1365-2656.2003.00678.x
en
British Ecological Society
Effects of fat reserves on annual apparent survival of blackbirds Turdus merula
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