FOOD DELIVERY TO NESTLING STORM-PETRELS - LIMITATION OR REGULATION

1. Temporal variation in food delivery to nestling British Storm Petre ls Hydrobates pelagicus was examined by repeated overnight weighing, t o determine whether provisioning rates were likely to be determined pr imarily by the availability of food to adults foraging at sea or by th e chick's immediate food requirements. 2. The interval between success ive feeds was short, indicating a relatively small foraging range. 3. There was a negative correlation between mean daily wind speed (consid ered to reflect foraging conditions) and the proportion of adults retu rning to feed their chicks (but not meal size) the following night, bu t this was heavily dependent on a few extreme values. There was no cor relation between wind speed and feeding frequency during more typical weather conditions. 4. Chicks' requirements for body maintenance incre ased with chick age, up to about 39 days post-hatching. This was paral leled by an increase in the amount of food consumed on nights when adu lts fed their chicks, but not feeding frequency. 5. There was evidence of regulation of feeding frequency in relation to recent feeding hist ory. 6. The finding that the frequency of feeding visits to the colony appears to be regulated in response to the chick's short-term nutriti onal requirements implies that the achieved feeding rates are below th e limits set by food availability and that the low rates of delivery m ay not be the result of low availability of food at sea.