Provisioning and growth in chicks of Wilson's storm-petrels (Oceanites oceanicus) on King George Island, South Shetland Islands

We present data on chick growth and chick feeding in Wilson's storm-petrel (Oceanites oceanicus) in a colony on King George Island, South Shetland Isl ands. Chicks were repeatedly weighed and the weight differences over 24 h w ere corrected for metabolic loss in order to obtain an estimation of meal s izes. Chicks were fed on 93% of the nights (n = 688 nights). The average me al size for a single feeding was 8.5 g. Chicks received on average 1.2 feed ings per night. These results are compared with data for this species from other locations. There was a trend for increased meal sizes from northern t o southern populations, parallel to an increase in the adult mass, indicati ng that Wilson's storm-petrels carry optimal meal sizes according to their body size and may take advantage of increased food abundance by increasing feeding frequencies. We describe chick growth and discuss the influence of egg size, hatching date and feeding frequency on chick growth. The egg size had a positive influence on tarsus growth and body mass of chicks. Later-h atched chicks started wing growth and finished mass growth at a younger age and reached lower peak masses, indicating that late chicks may adapt to th e restricted breeding season in their Antarctic breeding grounds by a more rapid development, but will fledge with a lower degree of development and l ess resources.