Diet of Westland Petrels Procellaria westlandica: the Importance of Fisheries Waste During Chick-rearing

SummaryThe diet of the Westland Petrel Procellaria westlandica was studied during the chick-rearing period (August—October) from 1993–96. Fish occurred in 92% of samples and formed 78.8 ± 6.5% by weight of the solid food brought back to the colony. Cephalopods were found in 32% of samples and contributed 18.7 ± 6.2% of solid food by weight. Crustacea occurred in only 4% of samples and contributed only 2.4 ± 2.4% of solid food by weight. During the part of the chick-rearing period in which the Hoki Macruronus novaezelandiae fishery was operating (August to mid-September), fisheries waste accounted for 80% of the fish found in samples and formed around 63% of the total diet at that time. After the Hoki season, fisheries waste accounted for only 31% of the fish found in samples, therefore contributing only around 25% of the total diet as birds switched to capturing more natural prey, or scavenged a wider variety of fish species, presumably from smaller, inshore fishing vessels.