Age Determination of Blue-Winged Teal

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Abstract
Primary feather length, markings on the greater secondary coverts, and the degree of bill spotting were evaluated as characters for use in the spring to distinguish 1st-year, blue-winged teal (Anas discors) females from older ones. The length of the 10th primary feather did not prove suitable to separate different aged females. Extreme primary lengths might be used to determine the age of some males. In females that have been through a postnuptial molt the greater secondary coverts have a more symmetrical, and more acutely angled, white, inverted "V"-marking. Any female with a "V" subjectively classified as good has gone through at least 1 postnuptial molt, and a female with no sign of a "V" on the coverts is a juvenile or yearling before her 1st postnuptial molt. By measuring the longest bill spot on the upper mandible of each known-age female, it was possible to determine the age of some female teal. Because the spots fade during the breeding season, no lower size limit could be set to delineate lst-year females at that time of year, but any nest-trapped hen with a spot longer than 10 mm was considered to be older than 1 year. Upper and lower limits were also established to distinguish some yearlings and 2-year-olds in the fall.

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