Nutrient sources for forest birds captured within an undisturbed petrel colony, and management implications
David J. Hawke A C and Richard N. Holdaway BA School of Applied Sciences and Allied Health, Christchurch Polytechnic Institute of Technology, PO Box 540, Christchurch 8140, New Zealand.
B Palaecol Research Ltd, PO Box 16-569, Christchurch 8042, New Zealand; and School of Biological Sciences and Department of Geological Sciences, University of Canterbury, Christchurch 8140, New Zealand.
C Corresponding author. Email: hawked@cpit.ac.nz
Emu 109(2) 163-169 https://doi.org/10.1071/MU08035
Submitted: 18 July 2008 Accepted: 8 December 2008 Published: 11 June 2009
Abstract
Where seabird breeding colonies occupy forested habitats, unusual nutrient links between marine and terrestrial ecosystems can occur. In such circumstances, the dietary characteristics of forest birds inhabiting pristine seabird colonies have rarely been investigated. In this study, carried out in a mixed-species colony of petrels (Procellariiformes), we measured the stable isotopic (δ13C, δ15N) signatures of individual feathers of New Zealand Bellbirds (Meliphagidae : Anthornis melanura melanura; n = 6) and Red-crowned Parakeets (Psittacidae : Cyanoramphus novaezelandiae novaezelandiae; n = 15). The δ15N of Parakeet feathers encompassed a wide range, from +7.1‰ to –0.9‰. From the high maximum δ15N, relative to global temperate forest foliage, we conclude that some Parakeets were feeding within the petrel colony where they were captured. However, the low minimum δ15N, relative to foliage from the petrel colony, implies that Parakeet isotopic composition could not be fully explained by potential dietary items from the petrel colony. Bellbird δ15N (range +3.4‰ to +9.6‰) was more enriched than that of Parakeets, consistent with their higher trophic level, but also consistent with a dietary intake consisting of items from both within and beyond the petrel colony. Bellbird isotopic ratios were strongly enriched in δ13C, which could be explained only by consumption of invertebrates with marine isotopic enrichment. The marine invertebrates could have been associated with breeding petrels, or have come from the littoral zone near the site of capture. The importance for both species of food sources both inside and outside of petrel colonies implies that petrel colonies offer foraging opportunities for forest birds but that the birds also use non-colony areas. Consequently, petrel colonies are integral parts of the wider terrestrial landscape which they inhabit.
Additional keywords: Adams Island, Anthornis melanura, Auckland Islands, Cyanoramphus novaezelandiae, introduced mammals, Meliphagidae, New Zealand, Psittacidae, Red-crowned Parakeet, seabirds, stable isotope analysis.
Acknowledgements
The research was carried out under permits issued by the Southland Conservancy, Department of Conservation (DoC). K. Walker (DoC) arranged the collection of samples and, with G. Elliott (DoC), gave a particularly helpful critique of a draft of the manuscript. J. Kemp and J. Armstrong collected the samples; collection was in accordance with New Zealand law pertaining to animal welfare. C. O’Donnell (DoC) and P. Sagar (National Institute of Water and Atmospheric Research Ltd) provided important background information, and journal referees encouraged us to explore in more detail the management implications of our results. Referee and editorial contributions to the clarity and focus of the paper are gratefully acknowledged. RNH acknowledges financial support from the New Zealand Foundation for Research, Science and Technology (Contract PLCX0201).
Anderson, A. (2005). Subpolar settlement in South Polynesia. Antiquity 79, 791–800.
Bartle, J. A. , and Sagar, P. M. (1987). Intraspecific variation in the New Zealand bellbird Anthornis melanura. Notornis 34, 253–306.
Fukami, T. , Wardle, D. A. , Bellingham, P. J. , Mulder, C. P. H. , Towns, D. R. , Yeates, G. W. , Bonner, K. I. , Durrett, D. S. , Grant-Hoffman, M. N. , and Williamson, W. M. (2006). Above- and below-ground impacts of introduced predators in seabird-dominated island ecosystems. Ecology Letters 9, 1299–1307.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Hawke, D. J. , and Holdaway, R. N. (2005). Avian assimilation and dispersal of carbon and nitrogen brought ashore by breeding Westland petrels Procellaria westlandica: a stable isotope study. Journal of Zoology 266, 419–426.
| Crossref | GoogleScholarGoogle Scholar |
Hobson, K. A. (1999). Stable carbon and nitrogen isotope ratios of songbird feathers grown in two terrestrial biomes: implications for evaluating trophic relationships and breeding origins. The Condor 101, 799–805.
| Crossref | GoogleScholarGoogle Scholar |
Wright, C. K. (2008). Ecological community integration increases with added trophic complexity. Ecological Complexity 5, 140–145.
| Crossref | GoogleScholarGoogle Scholar |