Survival of Radiomarked Canvasback Ducklings in Northwestern Minnesota

Authors

Carl E. Korschgen, Upper Mississippi Science Center
Kevin P. Kenow, Upper Mississippi Science Center
William L. Green, Upper Mississippi Science Center
Douglas H. Johnson, USGS Northern Prairie Wildlife Research CenterFollow
Michael D. Samuel, National Wildlife Health Center
Louis Sileo, USGS Northern Prairie Wildlife Research Center

Date of this Version

1996

Comments

Published in The Journal of Wildlife Management, Vol. 60, No. 1 (Jan., 1996), pp. 120-132.

Abstract

Duckling survival, an important factor affecting annual recruitment, has not been determined adequately for canvasbacks (Aythya valisineria). We investigated the magnitude, timing, and causes of mortality of canvasback ducklings from hatch to fledging at the Agassiz National Wildlife Refuge (NWR) in northwestern Minnesota during 1987-90. During the 4 years, 217 day-old ducklings were radiomarked and released in 52 broods. Another 141 ducklings were radiomarked at > 4 weeks of age. Survival was estimated with the Kaplan-Meier nonparametric estimator and the Weibull parametric model. Most mortalities occurred within 10 days after hatch. Total brood loss occurred in 18 (35%) of 52 broods released. The primary sources of mortality were predation, principally by mink (Mustela vison), and exposure to precipitation and cold temperature. For combined years, females had lower survival than males (P = 0.03). If the disparate survival between sexes of canvasbacks observed in this study is representative of canvasbacks in their breeding range, this phenomenon contributes to reduced reproductive potential and the male-biased sex ratio of the species.