DAVID E. SAMUEL Biology Department, West Virginia University, Morgantown, West Virginia 11
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determine whether wing length (measured on museum skins), tail length (measured on museum skins), breast color (observed in the field), or behavior (observed in the field) could be used to sex Barn Swallows. Differences in wingchord lengths of male and female study skins were not significant.
Outer rectrice lengths of male study skins were significantly longer than females; thus, tail measurements could prove quite useful as a sexing technique in the field. Differences in breast color (measured visually as buff, light orange, medium orange, or dark orange) could not be correlated with sex. Breast colors of 24 males which attempted to copulate with a mount placed in the field were equally buff, light orange, medium orange, or dark orange. Copulatory behavior was used to sex paint-marked birds in the field, and indications are that other behavior patterns, such as that of following, may also be useful. Usual field methods for sexing passerine species involve coloration, brood patch, or feather length. While carrying out a study on the breeding biology of Barn Swallows {Hirundo rustled) (Samuel, 1969), it was desirable to sex birds in the field without sacrificing them. Proposed methods for sexing Barn Swallows include differences in breast color (Bent, 1942; Chapman, 1912) and in tail length (Vietinghoff-Riesch, 1964). It was the purpose of this study to determine whether these or any other methods could be used to sex Barn Swallows. METHODS A total of 118 Barn Swallows was mist-netted during this study. These birds were captured in study areas near Bruceton Mills and near Terra Alta, Preston County, West Virginia. All birds were banded, and paint-marked for identification after release (Samuel, 1970), and some were also behaviorly sexed (based on copulation attempts on a mounted Barn Swallow) in the field. In addition to copulation, other behavior patterns which might be used to sex adult Barn Swallows were observed. Male birds follow females during activities around the barns, and while feeding, so observations were kept on perching and following in marked Barn Swallows where pairs had been sexed on the basis of earlier obof copulation attempts. Measurements taken at the time of banding were: (1) wing-chord length, measured by placing the carpal joint of the closed wing on a metric rule and pivoting the wing downward until the tip of the tenth primary touched the rule; (2) tail length, measured by inserting a metric rule to the base of the outer rectrice; and (3) breast color, measured visually as buff, light orange, medium orange, or dark orange. The accuracy of these color assignments was checked as marked birds were recaptured; four of 35 recaptured birds (14 percent) had been placed in the wrong category, but none had been misplaced by more than one category (e.g., light orange to dark orange). Measurements of wing length, tail length, and breast color were also made on known-sex museum specimens. These included 40 known-sex birds in the Carnegie Museum collections (Pittsburgh, Pennsy.vania). In addition, breast colors were recorded for those live males which were captured, which were observed in the field in pairs, and which attempted to copulate with the Barn Swallow mount. Manuscript received February 9, 1970. 2 Present address: Division of Forestry, West Virginia University, Morgantown, West Virginia.
DAVID E. SAMUEL Vol. 71 RESULTS AND DISCUSSION Wing-lengths measurments of study skins of male and female Barn Swallows were not significantly different (p>.05) (Table I). The lengths of outer tail feathers reportedly (Vietinghoff-Riesch, 1964) can be used to sex Hirundo in Europe. In this study, measurements of museum skins revealed that males did indeed have longer outer tail feathers than did females, so this method should give good results when sexing Barn Swallows in the field.
In terms of breast color, significantly more light-orange-breasted birds were observed, both as captures in the study areas and as study skins in the Carnegie Museum (Table II). Of pairs of birds observed perching together, more lightorange-breasted birds were observed (Table II). A mount of a female Barn
SEX DETERMINATION OF BARN SWALLOWS 127 Swallow was placed on a fence once per site visit and counts of attempted copulations were made. Males in the area immediately responded with copulation attempts, at which time breast color of these males was visually recorded (Table III). Because the sample size is small, no definite conclusions can be drawn. However, some birds with buff- and light-orange-colored breasts did attempt copulation. This does not support Bent (1942) and Chapman (1912), who report that male Barn Swallows have dark-orange breasts. Vietinghoff-Riesch (1964) has suggested that, in Europe, breast color differences may be due to a number of different races of Hirundo. However, the fact that male birds with differentcolored breasts were found in the same barn or seen paired makes the hypothesis doubtful. Rather, all the above data support the idea that breast color is not a good indication of sex.
No. 2 SEX DETERMINATION OF BARN SWALLOWS 127 Swallow was placed on a fence once per site visit and counts of attempted copulations were made. Males in the area immediately responded with copulation attempts, at which time breast color of these males was visually recorded (Table III). Because the sample size is small, no definite conclusions can be drawn. However, some birds with buff- and light-orange-colored breasts did attempt copulation. This does not support Bent (1942) and Chapman (1912), who report that male Barn Swallows have dark-orange breasts. Vietinghoff-Riesch (1964) has suggested that, in Europe, breast color differences may be due to a number of different races of Hirundo. However, the fact that male birds with differentcolored breasts were found in the same barn or seen paired makes the hypothesis doubtful. Rather, all the above data support the idea that breast color is not a good indication of sex. TABLE III The Number of Breast Color Classes For 24 Adult Male Barn Swallows Which A ttempted Copulation With A Taxidermy Mount Breast Color Class Number buff 4 >non significant difference light orange 8 >non significant difference medium orange 6 >non significant difference dark orange 6
DAVID E. SAMUEL Vol. 71 thesis that older birds have both darker breasts and longer tails. However, more data would be needed to demonstrate the validity of these hypotheses. ACKNOWLEDGMENTS Financial support was provided by the American Museum of Natural History through Frank M. Chapman Memorial Grants in 1967 and 1968. Additional support was provided by a National Science Foundation Summer Traineeship in 1967. The manuscript was typed by Miss Charlotte Lemley. This study would not have been possible without the constant support and advice of Dr. W. N. Bradshaw. LITERATURE CITED Bent, A. C. 1942. Life histories of North American flycatchers, larks, swallows, and their allies. U. S. Natl. Mus. Bull. 179: 538 p. Chapman, F. M. 1912. Color Key to North American Birds. D. Appleton and Co., New York. 356 p. Samuel, D. E. 1969. The ecology, behavior and vocalizations of sympatric Barn and Cliff Swallows in West Virginia. Unpublished Ph.D. dissertation, West Virginia Univ. — 1970. Banding, paint-marking and subsequent movements of Barn and Cliff Swallows. Bird Banding 41(2): 97-103. Vietinghoff-Riesch, A. 1955. Die Rauchschwalbe. Dunker und Humblot, Schleisheimer Strasse 68, Munchen 13, Germany. 302 p.
