The foraging range of Great Shearwaters (Ardenna gravis) breeding on Gough Island

Abstract

Ardenna shearwaters have among the most extreme foraging trips of any central place forager, yet little is known about the foraging range of the largest member of the genus, the Great Shearwater (Ardenna gravis). GPS loggers were deployed on 20 Great Shearwaters (10 males and 10 females) nesting on Gough Island in the South Atlantic Ocean during the incubation and chick-rearing periods, recording a total of 25 foraging trips. Foraging trip characteristics were similar between sexes during incubation, but males tended to forage farther west than females. During chick-rearing, all tracked birds alternated long and short foraging trips. Long trips (20.2 ± 2.3 days) were similar in duration to incubation trips (22.2 ± 5.3 days), but the birds travelled greater distances during chick-rearing (9257 ± 3249 km) than during incubation (6863 ± 2521 km). Some commuting birds sustained speeds > 100 km/h, with one bird covering almost 1000 km in 10 h. During incubation, birds mainly travelled southeast towards the Antarctic Polar Front, whereas chick-rearing birds travelled more widely. Our study provides new information on the distribution of Great Shearwaters while breeding.