Variation and Regulation of Meal Size and Feeding Frequency in Cory's Shearwater Calonectris diomedea

Abstract

We examined the pattern of chick feeding in Cory's shearwater Calonectris diomedea on Selvagem Grande by weighing 50 chicks at 4-h intervals throughout nine successive nights, then daily for a further 11 days (20 days in all). Meal sizes were estimated from the sum of positive mass increments recorded over 4-h intervals (SUM). Mass increments over 24-h (NET) were linearly related to SUMs by the equation NET = 0.83 SUM −40.1 (r 2 = 0.82). Individual meals fed to chicks averaged 74 g (SD = 26.4 g, range = 20 - 100 g). A mean of 79% of chicks were fed each night and the mean interval between feeds was 1.3 nights, with a maximum of four nights. There was little day-to-day variation in feeding rate, and no relationship with ambient light conditions over a half lunar cycle