Appendicular Myology of Kirtland's Warbler

Abstract

KIRTLAND'S Warbler (Dendroica kirtlandii) is listed as one of the endangered species in the Red Book of Rare and endangered fish and wildlife of the United States (Goodwin et al., 1966). The total population of this warbler is about 1,000 birds (Mayfield, 1962). Inasmuch as the complete appendicular myology has not previously been described for any member of the family Parulidae, it seems worthwhile to describe and illustrate the myology of the Kirtland's Warbler. I am indebted to Robert W. Storer and Harrison B. Tordoff of the University of Michigan Museum of Zoology for one adult Kirtland's Warbler, collected in Montmorency County, Michigan, 26 June 1935, by Milton B. Trautman. Four other specimens were birds that I had hand-raised from the nest (Berger, 1966). I also acknowledge my appreciation to Mrs. Barbara Downs, who prepared the final ink drawings. Dissection under a binocular microscope is essential for the study of the myology of a bird the size of Kirtland's Warbler (approximately 53/4 inches in length). A few of the wing muscles and the short toe muscles approach the minimum size for description by means of gross dissection, even with magnifications X20 and X30. When studying a specimen of Fregilupus varius (Berger, 1957), I discovered by using histological techniques that M. latissimus dorsi pars posterior and M. abductor digiti IV were rudimentary muscles, consisting of a thin layer of striated fibers in a sheet of fascia. For all practical purposes, such a is absent. The presence of rudimentary muscles may, however, be of special interest in certain studies, and the modified technique described by Berger (1956) is useful for making a quick preliminary determination of the presence of muscle fibers in fascia or ligament. The terminology of the muscles in this paper is that used by George and Berger (1966).