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Marine Ecology Progress Series

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MEPS 198:283-291 (2000)  -  doi:10.3354/meps198283

Variability in foraging in response to changing prey distributions in rhinoceros auklets

Gail K. Davoren*

University of Victoria, Department of Biology, PO Box 1700, Victoria, British Columbia V8W 2Y2, Canada
*Present address: Biopsychology Programme, Departments of Biology & Psychology, Memorial University of Newfoundland, St. John¹s, Newfoundland A1B 3X9, Canada. E-mail:

ABSTRACT: Variable time budgets and foraging behaviour were observed in a marine diving bird, the rhinoceros auklet Cerorhinca monocerata, in response to intraseasonal and interannual variations in prey abundance and distribution. Few studies have simultaneously measured the spatial dispersal of seabirds at sea, time budgets at sea and prey abundance and distribution. Time budgets and foraging behaviour were determined through visual scans. Prey abundance, estimated hydroacoustically during marine transects, was similar among years, but prey was dispersed over larger spatial areas in 1997 than in 1995 and 1996. Rhinoceros auklets were also dispersed over larger spatial areas in 1997 and fewer mixed-species feeding flocks were formed. In 1997, rhinoceros auklets increased the time spent foraging, decreased the recovery periods between successive dives, and were more strongly associated with prey at larger spatial scales. This suggested that auklets were working hard while foraging but were less successful at locating and maintaining contact with prey when prey was more dispersed. In 1996, there was a period (June 13 to 20) when fish schools were common near the surface, during which auklets spent more time foraging and formed more feeding flocks. This suggested that auklets were working hard to take advantage of this readily available prey. This paper illustrates the importance of behavioural plasticity and time budget flexibility for seabirds living in highly variable environments.

KEY WORDS: Seabirds · Time budgets · Risk-sensitive foraging behaviour · Predator-prey interactions

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