The purposes of this study were: (1) to obtain information on individual variation in the anatomy of the muscles and nerves of the leg of Tympanuchus cupido pinnatus (Greater Prairie Chicken), T. c. attwateri (Attwater's Prairie Chicken), T. pallidicinctus (Lesser Prairie Chicken), and Pedioecetes phasianellus jamesi (Sharp-tailed Grouse); (2) to determine whether or not the two species of the genus Tympanuchus differ constantly in the myology of the leg; and (3) to determine what constant differences in the myology of the leg exist between the two closely related genera Tympanuchus and Pedioecetes.

These particular birds were chosen because they are closely related, and closely resemble one another in habitats occupied and in patterns of behavior. It was desired to study examples that showed as few adaptive differences as possible among the grouse. Series of each of the three species of grouse were readily obtainable, making it possible to draw comparisons at the level of individuals, subspecies, species, and genera.

The study here reported on was begun in the spring of 1957 and was completed in the autumn of 1961.

Prior work on the muscles of the leg of birds has been reviewed by Hudson (1937) and Hudson, et al. (1959). Only papers dealing with the innervation of the leg in birds are reviewed below.

DeMan (1873) treated the nerves of Paradisea papuana, Corvus monedula, and the chicken; he also commented briefly on a few other species. Jhering (Ihering, 1873) briefly described the lumbosacral plexus in approximately a dozen birds, but illustrated only two. Gadow (1880) described the nerves in Struthio, Rhea, and Casuarius; his paper contains some excellent illustrations of nerves. Unfortunately, the text is marred by numerous confusing typographical errors. Carlsson (1884) described the nerves of Eudyptes chrysolopha, Alca torda, Mergulus alle, and Mormon arcticus. Gadow (1891) described the nerves in a study that included a large variety of birds, but published few illustrations. DuToit (1913) described the lumbosacral plexus of the chicken. Romer (1927) gave the innervation of the hip and thigh muscles in the chicken, but did not cover the lumbosacral plexus. Appleton (1928) gave the innervation, in various birds, only of those muscles of the hip and thigh that are supplied by the tibial and peroneal nerves; he did not include the lumbosacral plexus. Sudilovskaya (1931) described the nerves of Struthio, Rhea, and Dromaeus (Dromiceius). Unfortunately, his illustrations are almost useless as far as the nerves are concerned. Boas (1933) described the lumbosacral plexus in a large number of birds. His extensive account includes numerous good illustrations. Howell (1938) listed the innervation of the hip and thigh muscles in the chicken; he did not include the lumbosacral plexus. Fisher (1946) listed the innervation of the muscles of vultures, but did not include the lumbosacral plexus. Wilcox (1948) gave the innervation of the muscles of Gavia immer, but did not include the lumbosacral plexus. Fisher and Goodman (1955) described the nerves in the Whooping Crane. Papers by Chomiak (1950) and Yasuda, et al. (1959), both dealing with the chicken, were not examined.