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Body weight and composition dynamics of fall migrating canvasbacks

Journal of Wildlife Management

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Abstract

We studied body weights and composition of canvasbacks (Aythya valisineria) during fall migration 1975-77 on stopover sites along the upper Mississippi River near La Crosse, Wisconsin (Navigational Pools 7 and 8) and Keokuk, Iowa (Navigational Pool 19). Body weights varied (P < 0.001) by age and sex without interaction. Weights varied by year (P < 0.001) on Pools 7 and 8. Mean weights increased (P < 0.01) within age and sex classes by date and averaged 3.6 and 2.7 g daily on Pools 7 and 8 and Pool 19, respectively. Percent fat was highly correlated (P < 0.001) with carcass weight for each age and sex. Live weight was a good predictor of total body fat. Mean estimated total body fat ranged from 200 to 300 g and comprised 15-20% of live weights among age and sex classes. Temporal weight patterns were less variable for adults than immatures, but generally increased during migration. Length of stopover varied inversely with fat reserves among color-marked adult males. Variation in fat condition of canvasbacks during fall may explain the mechanism regulating population ingress and egress on stopover sites. Fat reserves attained by canvasbacks during fall stopover may have adaptive significance in improving survival by conditioning for winter.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Body weight and composition dynamics of fall migrating canvasbacks
Series title:
Journal of Wildlife Management
Volume
53
Issue:
2
Year Published:
1989
Language:
English
Contributing office(s):
Northern Prairie Wildlife Research Center
Description:
p. 431-441
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Wildlife Management
First page:
431
Last page:
441
Number of Pages:
10