Volume 46, No. 1

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Foraging ranges of incubating Sooty Terns Onychoprion fuscatus on Bird Island, Seychelles, during a transition from food plenty to scarcity, as revealed by GPS loggers


1Dept. of Geography and Environmental Science, Whiteknights Campus, University of Reading, Reading RG6 6AB, UK
2Pointe au Sel, Mahe, Seychelles
3PathTrack, Unit 3 Chevin Mill, Leeds Road, Otley LS21 1BT, UK
4WildWings Bird Management, 2 North View Cottages, Grayswood Common, Haslemere GU27 2DN, UK (


NEUMANN, J.L., LAROSE, C.S., BRODIN, G. & FEARE, C.J. 2018. Foraging ranges of incubating Sooty Terns Onychoprion fuscatus on Bird Island, Seychelles, during a transition from food plenty to scarcity, as revealed by GPS loggers. Marine Ornithology 46: 11 - 18

Received 30 May 2017, accepted 25 September 2017

Date Published: 2018/4/15
Date Online: 2018/1/8
Key words: bathymetry, chlorophyll concentration, food shortage, GPS tracking, Onychoprion fuscatus, Sooty Tern, seabird foraging, sea surface temperature, Seychelles


The foraging tracks of incubating Sooty Terns, nesting on Bird Island, Seychelles, were identified using global positioning system (GPS) loggers attached to the central pair of rectrices. By chance, our 2014 study covered a transition from food abundance to shortage. Incubation shifts during food abundance were mainly 1-2 d long but, at the height of food shortage, ranged from 4 d to 13 d, leading to temporary and permanent nest desertion by individuals left caring for the egg. The duration of foraging trips and the distance travelled also increased, from 151 km to 271 km for birds absent for 1-3 d, to 2 142-2 779 km by birds that were away from the colony for 4-10 d. This technique, coupled with spatial analyses that relate track paths and foraging locations to bathymetry, sea surface temperature, and chlorophyll levels, permitted more detailed investigations of the breeding use of their oceanic habitats. It also provided data to support and define areas to be recommended for Marine Protected Area status in Seychelles and elsewhere.


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