Supervisor

Dr. Tony Diamond:ACWERN and UNBF

Committee

Dr. Steve Heard, UNBF; Dr. Richard Elliot, Canadian Wildlife Service (cws)

Project Description

Seabirds are long-lived species that are top consumers in the marine ecosystem. They are conspicuous and accessible samplers of the oceanic environment, making them ideal indicator species to assess changes in the marine environment where they spend the bulk of their lives, and

interesting study subjects when exploring scientific questions (e.g., Cairns 1987; Burger and Gochfeld 2002; Diamond and Devlin 2003). This study will investigate the relationship of four species of seabirds with their prey in the Bay of Fundy over the past ten years.

Niche theory states that no two organisms can coexist in the exact same niche and make use of identical resources (e.g., Lack 1945; Hutchinson 1957; Leibold 1995). Boundaries between ecological niches can become nebulous during the summer breeding season of temperate/polar seabirds; many seabirds require similar breeding sites and typically a seasonal abundance of marine productivity can result in many organisms consuming the same prey species (Diamond 1983). Examining the composition and size of seabird prey at different temporal scales gives the opportunity to define the ecological niche held by the organism or challenge the concept of niche separation entirely. ACWERN (Atlantic Cooperative Wildlife Ecology Research Network) has collected data on the feeding and demography of four species of seabirds for ten summers on Machias Seal Island in the Bay of Fundy in order to further investigate our questions regarding seabirds and their relationship with the marine environment.

Machias Seal Island (MSI) is a 9.5-hectare island located in the mouth of the Bay of Fundy, 18 km southwest of Grand Manan Island, New Brunswick. The island is the breeding site of several seabird species during the summer months, four of which have been the focus of a long-term study initiated in 1995 by ACWERN at the University of New Brunswick (UNB) in conjunction with the Canadian Wildlife Service (CWS) (Diamond and Devlin 2003). The focal species include two terns- Arctic Terns Sterna paradisaea and Common Terns S. hirundo - and two alcids - Razorbills Alca torda and Atlantic Puffins Fratercula arctica.

This study will explore intra- and inter-seasonal variability in the feeding of these four species of seabirds, comparing and contrasting how the seabirds use prey resources over time and through a change in local available prey. The data we have show a possible dramatic shift since 2000; historically the four species have fed their chicks primarily Atlantic Herring Clupea harengus, but in recent years other species have become the dominant food item, including small crustaceans, specifically euphausiids (Charette et al. 2004). One question of interest is: does the change in prey species composition affect the reproductive performance of the four species of seabirds? Herring is a fatty, nutrition-rich fish (Massias and Becker 1990); however past work on the long-term study has shown that seabird productivity varies with percent water/fat content in herring, rather than the proportion of herring in the chick diet (Diamond and Devlin 2003). As more feeding data accumulate since the switch in prey, the amount of herring in the diet may correlate with reproductive success, unless herring are replaced by energetically-equivalent prey. By examining feeding and reproductive trends over the past ten years for all four species of seabird we can elucidate aspects of niche theory and increase our understanding of the complex relationships that seabirds have with the marine environment.

Literature Cited

Burger,J. and Gochfeld,M. 2002. Effects of chemicals and pollution on seabirds. In Biology of Marine Birds. Edited by E.A.Schreiber and J.Burger. CRC Press, Boca Raton, FL. pp. 485-526.

Cairns,D.K. 1987. Seabirds as Indicators of Marine Food Supplies. Biological Oceanography 5: 261-271.

Charette, Mathieu R., Black, Amie L., Devlin, Catherine M., Diamond, A. W, and Minich, Laura I. 2004. Machias Seal Island 1995- 2003: progress report. Atlantic Cooperative Wildlife Ecology Research Network, University of New Brunswick. Fredericton, NB.

Diamond,A.W. 1983. Feeding overlap in some tropical and temperate seabird communities. Studies in Avian Biology 8: 24-46.

Diamond,A.W. and Devlin,C.M. 2003. Seabirds as indicators of changes in marine ecosystems.
Environmental Monitoring and Assessment 88: 153-175.

Hutchinson,G.E. 1957. Concluding remarks. Cold Spring Harbor Symposium Quantatative Biology 22: 415-427.

Lack,D. 1945. The ecology of closely related species with special reference to cormorant (Phalacrocorax carbo) and shag (P. aristotelis). Journal of Animal Ecology 14: 12-16.

Leibold,M.A. 1995. Niche concept revisited: Mechanistic models and community context. Ecology 76: 1371-1382.

Massias,A. and Becker,P.H. 1990. Nutritive value of food and growth in Common Tern (Sterna hirundo) chicks. Ornis Scandinavica 21: 187-184.