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Marine Ecology Progress Series

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MEPS 678:171-182 (2021)  -  DOI:

Stable isotope record from a resident New Zealand seabird community suggests changes in distribution but not trophic position since 1878

M. J. Rayner1,2,*, B. J. Dunphy2, K. Lukies2,3, N. J. Adams4, M. Berg5, L. Kozmian-Ledward3, M. H. Pinkerton6, S. J. Bury6

1Auckland Museum, Private Bag 92018, Auckland 1141, New Zealand
2School of Biological Sciences, University of Auckland, 3A Symonds Street, PB 92019, Auckland 1142, New Zealand
3The Northern New Zealand Seabird Trust, 174 Ti Point Road, RD5, Warkworth 0985, New Zealand
4Environmental and Animal Sciences, Unitec Institute of Technology, PB 92025, Victoria Street West, Auckland 1142, New Zealand
5Centre for Animal Movement Research, Department of Biology, Lund University, Sölvegatan 37, Lund 223 62, Sweden
6National Institute of Water and Atmospheric Research, Greta Point, 301 Evans Bay Parade, Hataitai, Wellington 6021, New Zealand
*Corresponding author:

ABSTRACT: Globally, human population growth, its associated pollution and the vast scale of industrialised fisheries are having negative impacts on oceanic food webs, affecting top predators such as seabirds. We used stable isotope (δ15N and δ13C) analyses of feathers to investigate the contemporary structure and long-term changes in a near-shore community of 5 seabird species in northern Aotearoa New Zealand. Feathers were collected from museum specimens or live individuals (collected between 1878 and 2019) in Tīkapa Moana, the Hauraki Gulf, a marine habitat increasingly threatened by overfishing and urbanisation. To tease out the effects of baseline ecosystem versus seabird distributional changes, we analysed muscle isotope values of forage fishes collected over 43 yr (1976-2019) and provide isotopic data from contemporary prey species sampled within the region. Contemporary δ15N and δ13C values were consistent with existing data on diet and foraging distribution of the 5 seabird species. Values of δ15N declined in only 1 of 5 species studied, suggesting little change in the trophic position of the other species over time. However, δ13C values declined in 3 species, and a lack of change in the δ15N and δ13C values of forage fish suggests that this change is reflective of a behavioural shift in the distribution of the birds. However, changes in isotopic baselines over the sampling period cannot be ruled out and require further investigation. Our results demonstrate the value of stable isotope analyses of contemporary and archived samples as a cost effective, non-invasive method for monitoring coastal seabirds in a changing world.

KEY WORDS: Carbon and nitrogen isotope · Feathers · Euphausiids · Salps · Forage fish · Museum collections · Hauraki Gulf

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Cite this article as: Rayner MJ, Dunphy BJ, Lukies K, Adams N and others (2021) Stable isotope record from a resident New Zealand seabird community suggests changes in distribution but not trophic position since 1878. Mar Ecol Prog Ser 678:171-182.

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