Stable isotopes reveal opportunistic foraging in a spatiotemporally heterogeneous environment: bird assemblages in mangrove forests

Buelow, Christina A., Reside, April E., Baker, Ronald, and Sheaves, Marcus (2018) Stable isotopes reveal opportunistic foraging in a spatiotemporally heterogeneous environment: bird assemblages in mangrove forests. PLoS ONE, 13 (11). e0206145.

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Environmental heterogeneity can foster opportunistic foraging by mobile species, resulting in generalized resource and habitat use. Determining species' food web roles is important to fully understand how ecosystems function, and stable isotopes can provide insight into the foraging ecology of bird assemblages. We investigated flexibility of food choice in mangrove bird assemblages of northeast Australia by determining whether species' carbon and nitrogen isotopic values corresponded to foraging group classification described in the literature, such as groups of species that are omnivorous or insectivorous. Subsequently, we evaluated foraging group isotopic niche size, overlap, degree of individual specialisation, and the probable proportions of coastal resources that contribute to their collective diets. We found that mangrove birds are more opportunistic when foraging than expected from previous diet studies. Importantly, relationships between the dietary diversity of species within a foraging group and isotopic niche size are spatially inconsistent, making inferences regarding foraging strategies difficult. However, quantifying individual specialisation and determining the probable relative contributions of coastal resources to the collective diet of isotope-based foraging groups can help to differentiate between specialised and generalised foraging strategies. We suggest that flexibility in mangrove bird foraging strategy occurs in response to environmental heterogeneity. A complementary approach that combines isotopic analysis with other dietary information (collated from previous diet studies using visual observation or gut content analyses) has provided useful insight to how bird assemblages partition resources in spatiotemporally heterogeneous environments.

Item ID: 56499
Item Type: Article (Research - C1)
ISSN: 1932-6203
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Copyright Information: © 2018 Buelow et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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A version of this publication was included as Chapter 5 of the following PhD thesis: Buelow, Christina Amy (2017) Integrated assessment of ecosystem connectivity and functioning: coastal forest avifauna of northeast Australia. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Birdlife Australia, Birds Queensland, Ecological Society of Australia (ESA), Wet Tropics Management Authority (WTMA)
Projects and Grants: Birdlife Australia Stuart Leslie Bird Research Award, Birds Queensland Research Grant 2015, ESA Student Research Award 2015, WTMA Wet Tropics Student Research Grant 2015
Date Deposited: 05 Dec 2018 07:45
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310914 Vertebrate biology @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 100%
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