Sex in City Plants, Animals, Fungi, and More by Kenneth D. Frank

Author:Kenneth D. Frank
Language: eng
Format: epub
Tags: NAT026000, Nature/Plants/General, NAT001000, Nature/Animals/General
Publisher: Columbia University Press
Published: 2022-04-19T00:00:00+00:00

Four Sexes: white-throated sparrow (Zonotrichia albicollis)

A white-throated sparrow picks a mate from only one in four white-throated sparrows.

White-striped form, male or female.

White-striped form, male or female.

Tan-striped form, male or female.

Tan-striped form, male or female.

The term “four sexes” in the white-throated sparrow refers to color, behavior, and genetics rather than anatomy. The white-throated sparrow has four functional sexes: male and female white-striped, and male and female tan-striped. Males of a color form mate with females of the opposite color form. Either sex can be either color form. White-striped males mate with tan-striped females. Tan-striped males mate with white-striped females.1

White-striped males act aggressively toward any white-throated sparrow that sings. They chase away singing females—which are always white-striped—and mate with tan-striped females—which never sing. The less aggressive tan-striped male competes poorly against the white-striped male for tan-striped females. White-striped males sing four times more often than do tan-striped males. So the tan-striped males mate with the singing white-striped females, which white-striped males reject. The trill note of the white-striped female evokes copulatory excitation in tan-striped males.2

White-throated sparrows overwinter in cities but migrate in spring to breed in boreal forests.3 In contrast to cities, boreal forests offer this species space to accommodate four sexes, each with a different suite of traits and needs.

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