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Timing and condition-related effects on recapture probability, mass change and stopover length of spring migrating songbirds on a small Mediterranean island.

We investigated, at the intra-specific level, the effects of variables such as physical condition, time, date and year of first capture, on the recapture probability, on the probability of improving physical condition during stopover and on the minimum stopover length. Over 61,000 records from 14 species have been used, composed of capture/recapture collected in a period of seven years. The probability of a bird being retrapped increased for those individuals initially trapped later in the clay and with a lower physical condition. Also, the probability of improving energetic condition, during a stopover of at least two days, increased with worse energetic conditions at first capture. A longer stopover would allow improvement of the initial condition, even in the case of a small Mediterranean island with limited food resources. This might offer an opportunity for migrants to avoid situations of unbearable physical stress after the demanding crossing of the Sahara and Mediterranean.