EDUCATION

Ph.D. University of Guelph, 1997
M.Sc. University of Western Ontario, 1992
B.Sc. McGill University, 1990

GENERAL RESEARCH INTERESTS

CURRENT RESEARCH

Intertidal mudflat research:

My current research focuses on the factors controlling community structure on intertidal mudflats in the upper Bay of Fundy. The area is a critical staging area for Semipalmated Sandpipers (Calidris pusilla), which migrate through the region annually during late summer. Hundreds of thousands of birds use the mudflats each year, feeding heavily on the dominant invertebrate in the system, the amphipod Corophium volutator.

Shorebirds feeding in other systems have been shown to limit the abundance of their invertebrate prey, and sometimes produce indirect effects that cascade through entire communities. Effects are often especially strong when birds aggregate and feed heavily in a small area, and when communities are relatively simple. Therefore, in the simple mudflat communities of Bay of Fundy, it is possible that sandpipers, by feeding heavily on Corophium, may have strong top-down effects that contribute to the structure of the intertidal community. Alternatively, control of the system may be primarily bottom-up, resulting in a situation where abundance of birds is controlled by Corophium availability and in which bird predation generates few indirect effects in the community.

During summer 1999, I conducted manipulative experiments on a mudflat at Avonport, N.S. I used a combination of predator exclosures (to keep birds out) and fertilizer (to stimulate primary production) to determine which forces are most important in structuring the mudflat. Results of this experiment provided evidence of both top-down and bottom-up effects, but neither transmitted more than one trophic level. Transmission of effects across trophic levels was prevented by the compensatory activities of mud whelks (Ilyanassa obsoleta). This probably helps to stabilize the community in the face of variation in either bird abundance or nutrient availability. Recent movements of birds away from traditional feeding areas and onto new mudflats may therefore have little effect on mudflat community dynamics. More generally, these results demonstrate that compensatory activities that block trophic cascades can occur in simple communities, as well the in complex systems with which they are usually associated. This research was conducted in collaboration with Dr. Tony Diamond (ACWERN) and Dr. Peter Wells, Ecosystem Science Division, Environmental Conservation Branch, Environment Canada (peter.wells@ec.gc.ca and pwells@is.dal.ca). Funding is provided by the Canadian Wildlife Service through Environment Canada. Lab space and assistance was provided by the Acadia Centre for Estuarine Research.

I also detected a significant negative relationship between whelks and Corophium at Avonport, suggesting that it may be possible to predict Corophium abundance, and possibly bird predation in an area, by counting whelks. I tested the generality of this relationship by collecting sediment samples from four mudflats in the upper Bay of Fundy during summer 2000. Results confirmed the relationship between Corophium and whelks. I also detected a negative relationship between whelk abundance and bird predation, and a positive relationship between adult Corophium and bird abundance, indicating that we should be able to predict where birds will feed in a given year using information collected from the mudflat. Results of these surveys may also help to explain recent movements of migrating shorebirds throughout the Bay of Fundy. This research, being conducted in collaboration with Dr. Myriam Barbeau (UNB Biology), Dr. Tony Diamond, and Dr. Peter Wells, is ongoing. During summer 2001, we will be analysing sediment samples collected during 2000 in an effort to link abiotic properties to biotic properties in this system.

Seaduck - Blue Mussel Research:

Beginning in fall 2001, I will be involved in a project examining effects of seaduck (primarily Greater Scaup Aythya marila and Oldsquaw Clangula hyemalis) predation on cultured blue mussels in Prince Edward Island. Cultured mussels are attractive to ducks because of their thin shells and high tissue:shell ratio. In recent years, as mussel culture on PEI has expanded into traditional fall staging areas for migrating ducks, mussel farmers have experienced significant losses of stock as a result of duck predation. Our goal in this study is to find a way for mussel culture operations and migrating seaducks to coexist on PEI.

The initial phase of the project is intended to determine the feeding behaviour of ducks at a mussel culture site (e.g. timing of feeding, prey size preferences) and their effects on the mussel crop (e.g. extent of loss, mussel eaten versus those shaken off). Using this information, we will then develop and test strategies to mitigate losses without undue disturbance of ducks. Models will be developed to predict crop yield under different culture strategies. Using aerial survey data, we will also assess the overall relationship between ducks and mussel culture operations on PEI. This will enable us to determine the extent of the problem for farmers, and the threat (in terms of habitat loss) that culture operations pose for migrating ducks.

This research is being funded by AquaNet (a Network of Centres of Excellence programme), and is carried out in collaboration with Dr. Myriam Barbeau, Dr. Tony Diamond, and Dr. Greg Robertson (Canadian Wildlife Sevice). Additional support is being provided by the Canadian Wildlife Sevice, PEI Department of Fisheries and Aquaculture, and PEI Aquaculture Alliance.

PUBLICATIONS

Hamilton, D.J., Barbeau, M.A. and Diamond, A.W. 2003. Shorebirds, snails, and Corophium in the upper Bay of Fundy: predicting bird activity on intertidal mudflats. Canadian Journal of Zoology 81:1358-1366.

Hamilton, D. J. 2001. Effect of rockweed availability and duckling age on feeding behavior of Common Eider ducklings. Waterbirds. In press.

Crewe, T.L., D. J. Hamilton, and A.W. Diamond. 2001. Effects of mesh size on sieved samples of Corophium volutator. Estuarine, Coastal, and Shelf Science 53: 151-154.

Hamilton, D. J. 2000. Direct and indirect effects of predation by Common Eiders (Somateria mollissima) in an intertidal community under disturbed and undisturbed conditions. Ecological Monographs 70(1): 21-43.

Hamilton, D. J. 2000. Community-level interactions between birds and aquatic macrophytes: lessons for a rockweed harvest? pp. 25-29 in: Rangeley, R. W., and J. L. Davies. (Eds.). Gulf of Maine rockweed: Management in the face of
scientific uncertainty. Proceedings of the GPAC workshop, St. Andrews, N. B., 5-7 December, 1999. Huntsman Marine Science Centre Occasional report 00/1:94p.

Hamilton, D. J., T. D. Nudds, and J. Neate.1999. Size-selective predation of blue mussels Mytilus edulis by Common Eiders Somateria mollissima under controlled field conditions. Auk 116(2): 403-416.

Hamilton, D. J. 1998. Community consequences of habitat use and predation by common eiders in Passamaquoddy Bay. p. 94 in: Burt, M. B. D. and P. G. Wells (Eds.). 1998. Coastal Monitoring and the Bay of Fundy. Proceedings of the Maritime Atlantic Ecozone Science Workshop, St. Andrews, New Brunswick, November 11-15, 1997. Huntsman Marine Science Centre, St. Andrews, N. B. 196 pp.

Hamilton, D. J., C. D. Ankney, and R. C. Bailey. 1994. Predation of zebra mussels by diving ducks: an exclosure study. Ecology 75(2): 521-531.

Hamilton, D. J. and C. D. Ankney. 1994. Consumption of zebra mussels (Dreissena polymorpha) by diving ducks in Lakes Erie and St. Clair. Wildfowl 45:159-166.

Hamilton, D. J. 1992. A method for reconstruction of zebra mussel (Dreissena polymorpha) length from shell fragments. Canadian Journal of Zoology 70: 2486-2490.

Hamilton, D. J. and M. J. Lechowicz. 1991. Host effects on the development and fecundity of gypsy moth, Lymantria dispar L., reared under field conditions. Canadian Journal of Zoology 69: 2217-222.

How to contact me:

Diana Hamilton
Atlantic Cooperative Wildlife Ecology Research Network and Department of Biology
University of New Brunswick
Bag Service 45111
Fredericton, N.B.
E3B 6E1
Canada.

email: dhamilt2@unb.ca
phone: (506) 453-4594
fax: (506) 453-3583