Periodic weighing and the assessment of meal mass and feeding frequency in seabirds

Abstract

Although periodic weighing of chicks is used widely as a means to assess meal mass and feeding frequency in seabirds, there have been few critical assessments of its effectiveness. Using established methods, we were able to predict whether feeding had occurred with an accuracy of over 96% at nests where adult attendance was being monitored independently. This was despite the occasional provision of small meals which did not result in positive mass increments of chicks between weighings. However, information from repeat weighing could not be used to distinguish food delivery by both rather than a single parent within the weighing interval according to the relative sizes of mass increments. This may be because chicks are unable to cope with large meals from both adults because of gut capacity constraints. In addition, adults occasionally return from foraging trips with no food for the chick. These results have important implications for studies in which adult foraging trip durations are estimated solely using periodic weighing data, particularly in species with relatively short feeding intervals.