Katherine Shlepr

kate attempting to band a herring gull chick.
Master’s candidate
Department of Biology
University of New Brunswick
supervisor: Dr. Tony Diamond
committee: Drs. Graham Forbes and Karel Allard


At its core, Optimal Foraging Theory (OFT) predicts that individuals will adopt feeding strategies that maximize caloric intake while minimizing the amount of energy required to obtain those calories (Stephens et al. 2007). Herring gulls are well suited to test OFT because they are regionally abundant and because major aspects of their biology have long been studied. As a species, herring gulls are generalists, feeding on everything from garbage to fish to other birds. As individuals, however, they tend to specialize by relying on certain types of food to meet the bulk of their energy requirements (Tinbergen 1953, Ceia et al. 2014). Using gulls to examine the complexity of individual choice and of learned foraging strategy will improve our ability to understand, model, and predict foraging behavior in general.
In May 2014, collaborators from the Environment Canada, Acadia University, the University of New Brunswick, and the Mersey Tobiatic Research Institute successfully deployed 9 solar-powered GPS tags and 5 retrievable I-got-U tags on the backs of herring gulls nesting on Brier Island, Nova Scotia. The initial goal of the project was to assess where Brier Island gulls go to forage. For my Master’s research, I will continue this study by using a combination of GPS tagging, stable isotope analysis, and in-colony monitoring to explore the question: Does specialized foraging behaviour lead to differential nesting success in Herring Gulls that breed in the lower Bay of Fundy?


Herring gulls are some of the most conspicuous creatures in our marine landscape, but their populations are declining fast—in eastern North America, 50% in the last 30 years (Nisbet et al. 2013). Food availability is thought to be a major driver in both the rise and fall of our herring gull population, though the evidence supporting this hypothesis is pooled from a handful of studies spaced widely in geography and time (Hebert 1989, Robertson et al. 2001, Nisbet et al. 2013). Open landfills and fishery discards supplemented gull diet, which increased chick growth and over-winter survival in both young birds and adults (Goodale 2001, Weiser & Powell 2010). With the decline of the fishing industry and the covering of landfills after the 1980s, this source of food all but disappeared, and scientists have since observed major shifts in gulls diet (Stenhouse & Montevecchi 1999, Robertson et al. 2001). My project detailing the foraging behaviour of gulls in the lower Bay of Fundy provides necessary evidence to test the food hypothesis empirically.
When herring gull populations exploded regionally in the early 20th century (Drury 1973), the species was quickly labeled a nuisance—one that spreads disease and noisily invades our cities and beaches. Today, lethal control programs are limited to islands where predation or displacement by gulls significantly affects the health of puffins, terns, eiders, and other populations of conservation interest. How we approach gull control is important. Understanding the fitness ramifications of foraging choices may help to encourage management practices that ensure the conservation of all species (Finney et al. 2001, Guillemette & Brousseau 2001).herring gull


Ceia, F.R., V.H. Paiva, V. Fidalgo, L. Morais, A. Baeta, P. Crisostomo, E. Mourato, S. Garthe, J.C. Marques, J.A. Ramos. 2014. Annual and seasonal consistency in the feeding ecology of an opportunistic species, the yellow-legged gull Larus michahellis. Marine Ecology Progress Series 497: 273-284.
Drury, W.H. 1973. Population changes in New England seabirds. Bird-Banding 44: 267-313.
Finney, S.K., S. Wanless, M.P. Harris, & P. Monaghan. 2001. The impact of gulls on puffin reproductive performance: an experimental test of two management strategies. Biological Conservation 98: 159-165.
Goodale, M.W. 2001. Herring Gulls’ use of lobsterbait during the breeding season in Penobscot Bay, Maine. Master’s thesis, College of the Atlantic, Bar Harbor, Maine.
Guillemette, M. & P. Brousseau. 2001. Does culling predatory gulls enhance the productivity of breeding Common Terns? Journal of Applied Ecology 38: 1-8.
Hebert, P.N. 1989. Decline of the Kent Island, New Brunswick, Herring Gull, Larus argentatus, colony. Canadian Field-Naturalist 103: 394-396.
Nisbet, I.C.T., R.R. Veit,, S.A. Auer, and T.P. White. 2013. Marine Birds of the Eastern United States and the Bay of Fundy. Nuttall Ornithological Monographs, No. 29. Nuttall Ornithological Club, Cambridge, Massachusetts.
Robertson, G.J., D. Fifield, M. Massaro, & J.W. Chardine. 2001. Changes in nesting-habitat use of large gulls breeding in Witless Bay, Newfoundland. Canadian Journal of Zoology 79: 2159-2167.
Stenhouse, I.J. & W.A. Montevecchi. 1999. Indirect effects of the availability of capelin and fishery discards: gull predation on breeding storm-petrels. Marine Ecology Progress Series 184: 303-307.
Stephens, D.W., J.S. Brown, & R.C. Ydenberg. 2007. Foraging Behavior and Ecology. University of Chicago Press, Illinois.
Tinbergen, N. 1953. The Herring Gull’s World. Collins, London.
Weiser, E.L. & A.N. Powell. 2010. Does garbage in the diet improve reproductive output of Glaucous Gulls? The Condor 112: 530-538.


Shlepr, K.R. 2013. Temporal and spatial aspects of aggressive interactions in nesting gulls. Oral presentation. Waterbird Society annual meeting, Wilhelmshaven, Germany.

Shlepr, K.R. 2013. Ecology and conservation in northern British Columbia. Invited oral presentation. Senior Project Presentations, College of the Atlantic, Bar Harbor, Maine, USA.

Shlepr, K.R. 2012. Impact of Bald Eagle Predation on Herring Gull survivorship in Maine, USA. Poster presentation. North American Ornithological Council meeting, Vancouver, Canada

Shlepr, K.R. 2011. Effects of Bald Eagle predation on Herring Gull nesting colonies in Maine, USA. Oral presentation. Waterbird Society annual meeting, Annapolis, Maryland, USA.