Page:The Zoologist, 4th series, vol 4 (1900).djvu/100

 

ON SEXUAL DIFFERENCES IN THE WING OF
THE HOUSE-SPARROW (PASSER DOMESTICUS).

By Arthur G. Butler, Ph.D., &c.

 

In a short article on the wing of the Sky-Lark, which I published in 'The Zoologist' for 1898, I expressed my intention of noting the sexual differences in wing-structure of other species. Mr. C.H.B. Grant again assisted me with wings of three male and three female specimens of the domestic Sparrow; I already possessed five others, and subsequently Mr. F.W. Frohawk added to my collection. I therefore thought I could not do better than select this as an additional example in proof of the fact that, as a rule, the wings of male birds are better adapted to swift flight than those of their mates, thus enabling the former to overtake the latter when courting.

Of the six wings which Mr. Grant secured for me, all are carefully labelled, but in five of them the important note is added of the actual length of the bird in the flesh from which the wing was removed. As will at once be seen, this is a point of considerable importance, as it proves that, although individuals vary slightly in size, there is no great discrepancy in the total length of the sexes in the flesh. The following are measurements of three males:—

Females		1. Total length		63⁄8 inches.
		2.„„		61⁄4„
		3.„„		61⁄8„

Of two females the measurements are:—

Females		1. Total length		61⁄2 inches.
		2.„„		61⁄8„

Comparing the expanded wings of the sexes in the same specimens, we get the following interesting results:—

Males	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	1. Total length		41⁄2 inches.
		2.„„		33⁄4„
		3.„„		35⁄8„
Females	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Total length		31⁄2„
		„„		37⁄16„