Maximum dive depths of eight New Zealand Procellariiformes, including Pterodroma species

Abstract

Lightweight capillary tube depth gauges were attached to eight petrel species breeding at New Zealand colonies during the period 1998-2008.This paper presents the first information on the diving ability of Pterodroma petrels.Grey-faced Petrels, Pterodroma macroptera gouldi, recordedmaximum dives down to 23 m. Males (6.3 ± 6.3 m SD) dived deeper on average than females (3.6 2.5 m) during the incubationperiod but not significantly so (P=0.06). Breeding birds dived significantly deeper on average than non-breeders, and breeding males divedsignificantly deeper on average than non-breeding males. The two small Pterodroma species sampled, Pterodroma pycrofti and Pterodromanigripennis, only exhibited shallow dives down to 2 m but sample sizes were small. Sooty Shearwaters, Puffinus griseus, had mean maximumdive depths of 42.7 ± 23.7 m, with males (53.0 ± 17.3 m) diving significantly deeper on average than females (20.1 ± 20.4 m) duringthe incubation period. One male Sooty Shearwater dived to nearly 93 m, the deepest dive so far recorded in the order Procellariiformes.Flesh-footed Shearwaters, Puffinus carneipes, dived to 28 m, with a mean maximum dive depth of 13.6 ± 7.9 m. Hutton's Shearwaters,Puffinus huttoni, had a mean maximum dive depth of 23.0 ± 8.5 m (range 11.1-36.6 m). A single Fluttering Shearwater, Puffinus gavia,recovered with a dive gauge had dived to 29 m. Mean maximum dives made by Common Diving-Petrels, Pelecanoides urinatrix, of 10.9± 6.1 m (range 6.9-22.2 m) were shallower than results reported from other sites but may have been biased by gauge failures. Capillarygauges provide the best means we have at present to understand the diving capability ofsmall seabirds. While studies elsewhere have shownthese gauges may overestimate diving performance by about 10-15%, other factors identified in this study indicate that sometimes divingperformance will be underestimated using this simple technique.