Niche partitioning by three Pterodroma petrel species during non-breeding in the equatorial Pacific Ocean

Rayner, M.J.; Carlile, N.; Priddel, D.; Bretagnolle, V.; Miller, M.G.R.; Phillips, R.A.; Ranjard, L.; Bury, S.J.; Torres, L.G.. 2016 Niche partitioning by three Pterodroma petrel species during non-breeding in the equatorial Pacific Ocean. Marine Ecology Progress Series, 549. 217-229. 10.3354/meps11707

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Abstract/Summary

Niche divergence is expected for species that compete for shared resources, including migrants that occupy similar regions during the non-breeding season. Studies of temperate seabirds indicate that both spatial and behavioural segregation can be important mechanisms for reducing competition, but there have been few investigations of resource partitioning by closely related taxa in low productivity, tropical environments. We investigated niche partitioning in 3 gadfly petrel taxa, Pterodroma leucoptera leucoptera (n = 22), P. leucoptera caledonica (n = 7) and P. pycrofti (n = 12), during their non-breeding season in the eastern tropical Pacific Ocean by combining tracking data from geolocator-immersion loggers with remotely sensed environmental data in species distribution models (SDMs), and by comparing feather stable isotope ratios. The 3 taxa showed spatial partitioning: two foraged in the North Equatorial Counter Current and one in the South Equatorial Current. This reflected differences in their realised habitat niches, with significant taxon-specific responses to thermocline depth, sea surface temperature and bathymetry. There were also differences among taxa in activity patterns, and all birds spent a much larger proportion of time in flight at night than during the day, suggesting predominance of nocturnal foraging behaviour. Comparison of stable isotope ratios in feathers suggests that P. l. leucoptera and P. pycrofti mainly consume vertically migrating mesopelagic fishes, whereas the diet of P. l. caledonica also includes some lower trophic levels including crustaceans and squid. Unique insights can be gained from studies of the foraging ecology of tropical pelagic seabirds, in comparison with temperate and polar waters, and are urgently required for understanding and protecting tropical avifauna in key marine habitats.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.3354/meps11707
Programmes:	BAS Programmes > BAS Programmes 2015 > Ecosystems
ISSN:	0171-8630
Additional Keywords:	species distribution models, stable isotope analysis, niche, foraging ecology, seabirds, tropical Pacific
Date made live:	17 May 2016 13:16 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/513653

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