Some sex-ratio changes in relation to age of birds and mammals:

Species Percent Males Reference
Juvenilea Adult
Hungarian partridge 50 56 Keith (1958)
Bobwhite quail 51 62 Hickey (1955)
California quail 50 58 Emlen (1940)
Ruffed grouse 50 54 Dorney (1960)
Willow ptarmigan 54 60 Bergerud (1962)
Sharp-tailed grouse 49 55 Keith (1958)
Mallard 51.2 63.8 Bellrose et al. (1961)
Black duck 48.6 61.3 Bellrose et al. (1961)
Pintail 51.6 54.9 Bellrose et al. (1961)
Canvasback 44.0 56.8 Bellrose et al. (1961)
Scaup 49.7 61.4 Bellrose et al. (1961)
Starling 52 66 Davis (1959)
. . . .
Brown rat 51 41 Leslie et al. (1952)
Muskrat 57 50 Beer and Trux (1950)
Cottontail rabbit 50 46 R. A. McCabe (unpub.)
Elkb 52c 23 Cowan (1950)

a The term juvenile refers to birds during thier first fall or winter.

b Data from unhunted population where food was scarce.

c Juvenile = prenatal to 8 months old.


Adapted from a page on Sex Ratios.

Updated 05 August 1996