Blackbird (Turdus merula) Science Article 5
Fat reserves are stored energy that may help birds survive periods of harsh winter weather. This hypothesis predicts that annual apparent survival is higher for birds with large fat reserves than for birds with few or no fat reserves in winter. Blackbirds (Turdus merula Linnaeus) were ringed in central Italy from 16 November to 20 February during 1990-2001. Fat scores were recorded for each bird. We used these capture-mark-recapture data for 1703 blackbirds to estimate the effect of large fat reserves on annual apparent survival, while controlling for transients, using computer programs surviv and mark. Probability of birds retaining large fat reserves, or retaining few fat reserves, over 2 successive years was also estimated.
Mark W. Miller, Arianna Aradis and Giuseppe Landucci, Journal of Animal Ecology 72 (1), 127-132