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

Abstract

The diet of the Westland Petrel Procellaria westlandicawas studied during the chick-rearing period (August-–October) from1993–96. Fish occurred in 92% of samples and formed 78.8± 6.5% by weight of the solid food brought back to thecolony. Cephalopods were found in 32% of samples and contributed 18.7± 6.2% of solid food by weight. Crustacea occurred inonly 4% of samples and contributed only 2.4 ± 2.4%of solid food by weight. During the part of the chick-rearing period in whichthe Hoki Macruronus novaezelandiae fishery was operating(August to mid-September), fisheries waste accounted for 80% of thefish found in samples and formed around 63% of the total diet at thattime. After the Hoki season, fisheries waste accounted for only 31% ofthe fish found in samples, therefore contributing only around 25% ofthe total diet as birds switched to capturing more natural prey, or scavenged a wider variety of fish species, presumably from smaller, in-shore fishing vessels.