Foraging behaviour of chick-rearing rhinoceros auklets Cerorhinca monocerata at Teuri Island, Japan, determined by acceleration-depth recording micro data loggers

Flight and diving activity of rhinoceros auklets Cerorhinca monocerata breeding on Teuri Island, Japan, were monitored during the summers 1999 and 2000 using miniaturized time-depth and acceleration recorders. Birds made 14.5 dive bouts per day of on average 15.4 min duration, which consisted of on average 16.2 dives of 12.1 m depth and 42.7 s duration. Birds made 13.8 +/- 7.3 flight bouts per day, which lasted on average 11.5 +/- 4.5 min. Daily total flight duration was 2.7 +/- 1.7 h (range 54 s-5.1 h) and the mean potential foraging range was estimated to be 87 km (maximum 164 km). Most birds stayed at the colony or rested on the water surface during the night. Rhinoceros auklets dived more actively in early morning and in late afternoon than during mid-day. Compared to results from studies of time allocation in other alcids species, rhinoceros auklets spent longer time flying (3.3 hd(-1)) and resting on water (13.1 hd(-1)), and less time diving (3.1 hd(-1)) and staying at the colony (4.4 hd(-1)). These foraging patterns are probably related to the nest attendance pattern of rhinoceros auklets, i.e. leaving the colony early in the morning, staying at sea all the day and returning to the colony in the evening to provision their chicks.