NESTLING FEEDING STRATEGY OF THE BRITISH STORM-PETREL HYDROBATES PELAGICUS IN A MEDITERRANEAN COLONY

The pattern of chick feeding of the British storm-petrel Hydrobates pe lagicus in a Mediterranean colony was examined by weighing chicks at 2 4-h intervals on different days during the nestling period. In order t o calibrate daily mass increments (NET) against number of feedings, da ily mass changes of chicks were regressed upon the sum of positive mas s increments recorded overnight (SUM) during four nights. The average meal size delivered to chicks per night by one parent was 3.5+/-1.3g o r 12% of adult weight. This was insufficient for sustaining constant c hick mass during a day. On average 85% of chicks were fed each night, and the mean interval between feeds was 1.2+/-0.5 nights. Nightly feed ing frequencies differed among days, but this night-to-night variation was not related to meteorological conditions. Both food requirements necessary for chick body maintenance (zero-growth) and meal size were relatively constant for ages up to 59 days. However, feeding frequency decreased throughout the fledging period, accounting for age-specific variation in growth rates until fledging. Food requirement and feedin g patterns at Benidorm were different from North Atlantic colonies. No ne the less, growth patterns were almost identical, suggesting adjustm ent to maintain chick body mass al a determined level, as food deliver y to nestling appears to be regulated to chicks' nutritional requireme nts.