Feeding behavior and modeled energetic intake of common loon (Gavia immer) adults and chicks on small lakes with and without fish |
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Authors: | Beverly A Gingras Cynthia A Paszkowski |
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Institution: | (1) Department of Biological Sciences, University of Alberta, T6G 2E9 Edmonton, AB, Canada;(2) Canadian Wildlife Service – Prairie and Northern Region, Environment Canada, #200 4999 – 98 Avenue, T6B 2X3 Edmonton, AB, Canada |
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Abstract: | We examined the behavior of common loons, Gavia immer (Brünnich), breeding on small, shallow lakes in central Alberta, Canada that were naturally fishless or contained only small-bodied
fishes (minnow lake). For both lake types, adults spent >90% of their time on the nesting lake and >50% of their time foraging.
Adult loons on fishless lakes dove more frequently, but dives were of shorter duration than loons on lakes with fish. On two
intensively studied fishless lakes, adults fed chicks macroinvertebrates, particularly leeches, whereas on a focal minnow
lake, fish made up >70% of prey items delivered by adults. Chicks >36 days of age on a minnow lake spent >50% of their time
foraging, whereas older chicks on fishless lakes were highly dependent on food provisioning by adults. Models based on observed
foraging patterns indicated that prey size was a better predictor of success in meeting energetic requirements than was feeding
behavior (e.g., dive rate, dive success). For most models, estimated energetic intake was higher for loons on minnow lakes
than on fishless lakes. Our behavioral observations and model results are consistent with surveys in central Alberta that
indicate that breeding Common Loons frequently establish territories on small lakes, but that chicks hatched on lakes completely
lacking fish rarely fledge and only if sufficient large invertebrates such as leeches are available. |
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Keywords: | chick behavior common loon diet energetic models foraging Gavia immer |
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