Northern Prairie Wildlife Research Center
This publication contains procedures used by the U.S. Fish and Wildlife Service to determine the species, sex and age composition of the harvest of North American ducks using detached wings contributed by hunters. Original studies of the use of duck wings for this purpose began in 1958 and were led by the author and A.D. Geis. Others contributing to these studies include R.L. Croft, E.M. Martin, A.N. Novara, L.D. Schroeder, M.G. Smart, and M.F. Sorensen. Major suppliers of known-age specimens include: W. Anderson, R.S. Billard, A.J.Erskine, D. Hall, A.S. Hawkins, C. Hoffpauir, L.R. Jahn, R. L. Jessen, F.B. Lee, J.J. Lynch, R.K. Martinson, D.P. Olson, R.P. Osbolt, C. Ritcey, R.N. Smith, H.E. Spencer, V.D. Stotts, and J. Takekawa. R.I. Smith edited the text, A.J. Godin prepared Figure 2, Larry Ketchum Photography took the pictures, and R.E. Cummins typed the manuscript.
The Waterfowl Parts Survey became the means by which large samples of duck wings were obtained. This survey became national in scope in 1961. Collection of goose tails was added to the survey in 1962. Packages of envelopes are mailed to selected hunters who return wings from shot ducks and tail feathers from shot geese by mail to collection points throughout the United States where they are examined to determine species, sex, and age.
For readers who are interested in more detailed information on the development and testing of procedures described in the following pages, copies of a more technical report, which was prepared by the author, are available by writing to Waterfowl Harvest Surveys, U.S. Fish and Wildlife Service, 10800 Laurel-Bowie Road, Laurel, Maryland 20708-3600. That report, titled 0bservations on Sexing and Aging Ducks Using Wings, makes several points that must be understood by anyone who plans serious use of these techniques. The procedures presented here vary among species in the degree to which they accurately identify the age and sex of duck wings. Accuracy varies according to skills of the observer. Some individuals become highly skilled after examining large numbers of duck wings, while other individuals never develop the ability to detect subtle differences in feather texture and feather quality with high levels of proficiency. Levels of skill will decline if techniques are not practiced with regularity.
Terminology related to age must be clarified. An immature wing possesses one or more characteristics known to be associated with ducks hatched in the most recent nesting season. Since the term immature often refers to maturing processes not related to plumage, juvenal might have been more appropriate. Nevertheless, after 30 years of use in this context, introducing another age designation would serve no purpose. All wings not possessing characteristics associated with the most recent hatch are classified as adult except those of yearling male eiders which are identified as being from sub-adults.
To determine the species, age, and sex of ducks from detached wings, a worker must be familiar with the various feather groups. The first step is to determine the species represented. A key to species is included as an appendix to this publication. Usually, slight differences in feather shape, color, pattern, wear, or replacement are sufficient during the fall and winter to separate immatures from adults. Age determination is a step-by-step search for one or more traces of immature plumage. Wings on which no traces of immaturity can be found, or in some cases those that have positive adult characters, are considered to be from adults.
During their first fall and winter immatures of many of the more common species of ducks molt certain wing-feather groups located near the body and replace them with adult-type feathers. Those feathers that are replaced include the tertials, greater tertial coverts, post humerals, and scapulars. Scapulars are of limited use in classifying wings because most hunters do not include scapulars on the wings they remove. Tertials, as defined here, are actually the more proximal secondaries, which are generally different in size, shape, and color from their more distal counterparts. These feathers are often sexually dimorphic and usually molt with adjacent body feathers. Post humerals are feathers attached to the humerus. They lie between the tertials and scapulars. They usually molt with adjacent body feathers. Greater coverts are the first row of feathers overlying the flight feathers, identified by the particular feathers they cover as primary, secondary, or tertial coverts. Greater tertial coverts are those greater coverts that overlie the tertials. They are designated separately because they are sexually dimorphic in adults of several species and often molt with the adjacent body feathers. The degree to which these feathers are replaced is quite variable, even among closely related species. Southern nesting duck species may initiate upperwing molts in the fall rather than in the spring. Fall wing molting occurs among wood ducks, mottled ducks, and whistling ducks. Such molting reduces the accuracy of immature wing identification in the fall and winter.
Male wings on most North American ducks are slightly larger than those of females. For a few species, this difference is large enough to permit separation of the sexes using wing measurements. The procedure for measuring duck wings applies to both fresh wings and wings with varying degrees of stiffness, as they are commonly received through the Waterfowl Parts Survey. To ensure uniformity, all measurements are made using a standardized procedure and measuring board. Measurements are referred to as wing notch-length.
Tables have an advantage over keys in that the color, shape, or texture of a particular group of feathers can be compared on one page across the four age and sex categories. Unlike keys, tables do not lead one directly to the answer. Despite this limitation, most people prefer tables to keys. Therefore, tables are used in this publication to present information on individual species. Wing characteristics are not always listed in the same sequence for each species. They are listed in the sequence in which they can be most efficiently used. A brief narrative, which identifies the most frequently used wing characters in a table, accompanies most tables.