Some Population Mechanics of the American Coot

Abstract

This paper is concerned with the annual mortality rate, age composition, and migratory distribution of the population of American coot (Fulica americana) contributing to the hunting kill in the northern Mississippi Flyway. It also evaluates three possible aging techniques and one sexing technique. Most studies of the coot (Sooter, 1945; Gullion, 1954; Kiel, 1955; and others) have dealt with the local breeding activity of the species, its large clutch size, and its high nesting success. Kiel and Hawkins (1953) described the status of the coot in the Mississippi Flyway on the basis of relative kill and winter inventory. With the exception of the mallard (Anas platyrhynchos), the coot has in recent years generally exceeded each species of waterfowl in numbers bagged in the Mississippi Flyway (Williams, 1953; Crissey, 1954, 1955, 1956, 1957). This status in the bag indicates a potential need for management of the species and for such basic information as estimates of the population's productivity and over-all mortality. Reeve and Pimlott (1950) have attempted to obtain an age and sex ratio for coots bagged at Lake Puckaway, Wisconsin. They found that some females possessed small bursae and adult-appearing ovaries. As the observed percentage of juveniles (90 per cent) seemed too high for normal production, these authors suggested differential migration by age groups. Working with small samples, Gullion (1952) was unable to demonstrate regression of the bursa with age or season. As an alternative method of aging, he suggested the use of tarsal color, and found a reasonable percentage of young (79 per cent in a sample of 79) in a California population. The further testing of this tarsal-color method and the determination of age structure in the bag were important objectives of the study reported here.