Machias Seal Island (MSI) is a 9.5 ha, treeless island located in the Gulf of Maine, at the mouth of the Bay of Fundy. It is designated a Migratory Bird Sanctuary and managed by the Canadian Wildlife Service because it is the breeding grounds of a large number of seabirds, including both Arctic and Common Terns.

Since 1995 Dr. Antony Diamond, of the University of New Brunswick (UNB) and the Atlantic Cooperative Wildlife Ecology Research Network (ACWERN), and his graduate students have been conducting research on the seabirds of Machias Seal Island. The goal of this research is to examine how seabirds might be used as bioindicators of marine ecosystems.

Despite extensive study on MSI of the breeding biology and chick diet characteristics of both tern species (1), Arctic Tern time budgets (2) and metapopulation dynamics (3), systematic investigation of their foraging grounds has yet to be done. Foraging areas of other tern colonies have been studied, although most of the information available is from research on Common Terns in Europe or the Great Lakes (4,5).

Because of this paucity of data, my study aims to determine were Arctic and Common Terns nesting on MSI find their food, and what physical and biological features are characteristic of their foraging grounds. I am also looking into how these areas might change according to nest status (incubation of eggs, chick-rearing, or failed nest).

The field work for this study was conducted during the summers of 2004 and 2005. The first summer was used to gather preliminary data and refine techniques for the following field season. In 2005, Arctic and Common Terns were fitted with radio transmitters attached to their bands (6), and were tracked from an airplane.

Preliminary results suggest that in 2005 Arctic and Common Terns nesting on MSI were foraging in areas with very similar characteristics, indicating that little competition between these closely related species was evident at the scale of the analysis (~3400 km2). Additionally, neither species foraged in areas with characteristics significantly different from characteristics of the entire habitat available for feeding. This suggests that, at this scale, terns were foraging at random, and not in response to the physical or biological variables inspected.
Further investigation should include examining tern responses to these variables at different scales, as well as their response to prey availability at different scales.

References

(1) Charette, M. 2005. Variation in the Breeding and Wintering Ground Diets of Sympatric Nesting Common and Arctic Terns. Unpublished M. Sc. Thesis. University of New Brunswick, New Brunswick.

(2) Paquet, J. 2001. Time-Budget Flexibility of Breeding Arctic Terns (Sterna paradisaea): An Investigation of the Behavioral Buffer. Unpublished M. Sc. Thesis. University of New Brunswick, New Brunswick.

(3) Devlin, C.M. 2006. Birds crossing borders: A population study of Arctic Terns (Sterna paradisaea). Unpublished Ph.D. Thesis. University of New Brunswick, New Brunswick.

(4) Becker, P.H., Dietrich, F., and Sudmann, S.R. 1993. Temporal and spatial pattern of Common Tern (Sterna hirundo) foraging in the Wadden Sea. Oecologia 93: 389-393.

(5) Burness, G.P., Morris, R.D., and Bruce, J.P. 1994. Seasonal and annual variation in brood attendance, prey type delivered to chicks, and foraging patterns of male Common Terns (Sterna hirundo). Canadian Journal of Zoology 72: 1243-1251.

Funding Acknowledgements

Science Horizons

New Brunswick Wildlife Trust Fund