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Use of Anthropogenic Foods by Glaucous Gulls in Northern Alaska
Use of Anthropogenic Foods by Glaucous Gulls in Northern Alaska
I started working toward my MSc with a pilot field season in 2007 and graduated in May 2010. My major advisor at the University of Alaska Fairbanks was Dr. Abby Powell (now at the University of Florida), and we collaborated closely with the Alaska North Slope Borough and the US Bureau of Land Management.
The Arctic hosts a fascinating ecosystem, where conditions are harsh but specialized organisms thrive. Any disruption to the balance can have far-reaching consequences. Like many gulls, Glaucous Gulls (Larus hyperboreus) are believed to benefit from association with human activity, primarily through consuming garbage - an easy, abundant, high-calorie food source. Glaucous Gulls are also major predators in the Arctic and have the potential to affect population dynamics of a variety of prey species, including threatened birds. Development of the Arctic Coastal Plain of Alaska is continuing, especially for energy production, so more food waste may become available. If food waste increases populations of scavengers such as gulls, and if this translates into higher predation pressure on natural prey species, the persistence of species that are already vulnerable may be further threatened.
Caribou
Collared lemming
Stilt Sandpiper chick
Polar bear and Long-tailed Ducks
My study was the first in northern Alaska to examine how access to garbage may benefit gulls and what prey species could be affected by an increase in the local Glaucous Gull population. I recorded gull diet and reproduction at several colonies in industrial, residential, and undeveloped areas of northern Alaska.
I found a positive relationship between the amount of garbage in diet and the number of chicks produced per pair, suggesting that garbage may cause gull population growth. About half of Glaucous Gulls disperse to breed away from their natal site, so those "extra" offspring will grow up to eat natural food (rather than garbage) and therefore add to predation pressure on prey species.
In addition to garbage, Glaucous Gull prey includes small mammals such as lemmings and voles, birds, and fish. I was able to identify about 30 bird species (eggs, chicks, and adults of shorebirds, waterfowl, ptarmigan, and songbirds) in gull diet samples, half of which are declining or otherwise of conservation concern. Garbage management practices such as incinerating garbage could help limit the benefit gulls receive from current or future development, thus helping to protect the sensitive prey species.
Float profile of a Glaucous Gull egg in water as it ages (click to enlarge).
Some examples of Glaucous Gull diet samples are pictured here (not to scale). I examined about 3000 samples but it was never boring as every one was different!
From top left: a pellet of lemming remains, a wing from a young shorebird, fish bone, fragment from the bottom of a large glass bottle (swallowed and regurgitated by a gull!), plastic that was eaten along with food waste.
Bottom row from left: an arctic ground squirrel skull, adult Dunlin leg (banded by a USFWS project near Barrow), and Greater White-fronted Goose head (probably scavenged from human hunters).
Published manuscripts detailing my findings are listed under the "Publications" link to the left.
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