Adelie penguins exhibit a unique form of behaviour known as the feeding chase, whereby a parent is chased by its creche aged chicks before feeding them. The brood reduction hypothesis proposes that feeding chases lead to preferential feeding of one chick when food is scarce. The contradictory brood maximisation hypothesis suggest feeding chases serve to distribute food evenly amongst chicks ... removing the effects of sibling competition. The grounding of the iceberg B-15 created a natural experiment making it difficult for penguins on Ross Island to access food. The function of feeding chases in adelie penguins was investigated by observing all feeding chases in the Northern rookery of Cape Bird.
Detailed behavioral observations were conducted over 8-10 days of feeding chases by creche-stage chicks including observations of numbers of chicks involved in the chases, distance traveled, distance between chicks, distances to adults, number of feeding bouts, identity of chick being fed, time between feeds and any interference from other chicks or other adults. Data from a fenced subcolony with a weighbridge was obtained to analyse attendance patterns and foraging trip durations of adult penguins and determine the amount of food delivered to chicks. Repeated body mass and morphometric measurements of 10 chicks in two chick broods was conducted to determine if one chick was benefitting at the expense of the other. Transects of the colony were walked in order to determine the proportion of one and two chick feeding chases occurring within and outside sub-colonise. Visits were also made to the adelie penguin colonies of middle and Southern rookery, Cape Bird, Cape Royds and Cape Crozier to make counts of the proportion of chicks creching, the adult:chick ratio, and where possible the proportion of one and two chick broods. Measurements were repeated in the following season after the iceberg B-15 had moved away to compare the results between years and the effects of food limitation on feeding chase behaviour.