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Site selection and foraging behavior of Aleutian Canada geese in a newly colonized spring staging area

The once endangered Aleutian Canada goose (Branta canadensis leucopareia) population made a dramatic recovery and was reclassifi ed from endangered to threatened in 1990 and removed from the threatened species list in 2001. In 1997 the birds began using a new spring staging area adjacent to Humboldt Bay in northern California. The new staging area, primarily dairy pastureland, is located ~150 km south of the population’s traditional spring staging area. Numbers increased in the new area from 1997, and peaked at 19,000 individuals (~50% of the total population) in early March 2002. In the northern Humboldt Bay staging area, foraging sites were located within 1 km of the bay’s associated tributaries. Forty-fi ve percent of goosedays were on pastures characterized as green (>95% green grass) with short to medium grass height (13–30 cm) and with some standing water, which represented 15% of the available habitat. Older pasture of medium grass height (30–60 cm) with standing water represented only 2% of available habitat but was the second most frequently used habitat (25%). At night the geese roosted initially on a pasture that was surrounded by narrow tributaries and later on a temporarily fl ooded pasture located behind large dunes that provided shelter from prevailing oceanic winds. A comparison between farms that did and did not attract the geese indicated that geese favored habitats with a larger percent cover of water (fresh or brackish) and those near to bodies of fresh water >750 m2. The geese spent 87% of the observed periods foraging on pasture plants. The continual increase in abdominal fat score indices over 90 days indicated that the geese were apparently acquiring reserves beyond requirements for daily maintenance energy.

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