Control of the Sex Characters in the English Sparrow, Passer domesticus (Linnaeus)

Abstract

I. The Male. A series of experiments was carried out to determine the nature of the control of the sex characters, particularly plumage, of the English Sparrow. Previous studies have established that the secondary sexual characters, including plumage, of various breeds of domestic fowl, ducks and pheasants are under the influence of the gonads.In the first experiment 52 male birds (35 adult and 17 immature) were castrated. At the time of the operation feathers were plucked from areas showing sexual dimorphism. The regenerated feathers were always of the male type. The capon assumes the normal male plumage and in this respect is similar to domestic fowl.The bill of the adult male during the breeding season is blue-black in color but during late August and early September the bill becomes a light horn color. This light color is retained during the winter but with the approach of the breeding season the bill again takes on the black color. When a male with a black bill is castrated the color changes to a lig...