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Body Condition, Food Habits, and Molt Status of Late-Wintering Ruddy Ducks in California

William L. Hohman, C. Davison Ankney and Douglas L. Roster
The Southwestern Naturalist
Vol. 37, No. 3 (Sep., 1992), pp. 268-273
DOI: 10.2307/3671868
Stable URL: http://www.jstor.org/stable/3671868
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Body Condition, Food Habits, and Molt Status of Late-Wintering Ruddy Ducks in California
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Abstract

We studied body condition, food habits, and molt status of late-wintering ruddy ducks (Oxyura jamaicensis) using drainwater evaporation ponds in the southern San Joaquin Valley, California. Levels of body fat and protein were similar by sex but varied by age (adults greater than immatures). Masses of breast and leg muscle protein were greatest in adult males and lowest in immature males, but similar in adult and immature females. Fat and protein levels in late-wintering ruddy ducks were independent of their body size. We detected no differences among sex-age classes in the proportion of animal foods consumed. Aquatic invertebrates composed >85% of the diet; midge larvae (Diptera: Chironomidae) and brine flies (Diptera: Ephydridae) were the principal taxa consumed. Molt score by feather region and overall molt score did not vary by sex or age. Light to moderate molt (<25 to 50% molting feathers) was recorded in all feather regions. High levels of body fat and protein were attributed to premigratory hyperphagia and consumption of foods with a high protein:energy ratio.

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