both this species and in Little Egrets, some individuals participate in same-sex activity noticeably more often than others. In addition, homosexual activity comprises a greater proportion of “extramarital” sexual activity for some males than for others.
Nonreproductive and Alternative Heterosexualities
As described above, “extramarital” or promiscuous heterosexual copulations occur commonly in all four of these species. In Cattle Egrets, as many as 60 percent of all mountings are by males on females other than their mates, while in Gray Herons such matings account for more than 12 percent of all sexual activity. Nearly a third of all Little Egret copulations are promiscuous. In fact, many copulations in this context are actually rapes, since the female is not a willing participant (although in both Cattle and Little Egrets, females may also consent to such matings). Up to 7 percent of Cattle Egret eggs may be fertilized by a male other than the bird’s (social) father; however, many “extramarital” copulations are nonprocreative, since almost a quarter of all such matings take place when the female is already incubating her eggs. In addition to stepparenting of birds fathered by other males, several other alternative family arrangements occur: Cattle Egret trios of two females and one male may raise a family, while foster-parenting sometimes occurs when females lay their eggs in nests of other birds, including other species of Egrets and Herons.
Several mating behaviors in these species indicate that not all aspects of heterosexuality revolve around breeding. Cattle Egrets sometimes mate when fertilization is not possible, for example during incubation or chick- raising. And up to 14 percent of copulations between pair members may be “incomplete” in the sense that no genital contact or sperm transfer occurs—sometimes because the male is apparently not “interested” in mating even though his female partner is. In Little Blue Herons, some males copulate with females and yet remain “single” (i.e., do not pair-bond with them), while other males never pair with a female during the entire mating season. REVERSE mounts (females mounting males) also occur in Cattle Egrets, and in polygamous trios this sometimes results in a “pile-up” of three birds (one female mounting the second female who is mounting the male).
A number of violent and counterreproductive behaviors can make life harsh for young Egrets and Herons. In Little Blue Herons, infidelity often leads to abandonment of the nest by one or both partners (in part because eggs may be broken during the promiscuous sexual activity). Following a partner’s injury, male Cattle Egrets have been known to destroy their own eggs and desert their mates for a new female. Male Gray Herons also occasionally destroy their eggs by stabbing at them. Nest and mate desertion (especially by females) are common in Little Egrets as well. Often the remaining bird will successfully raise the chicks as a single parent; sometimes, though, the chicks die as a result of desertion. If a single father pairs with a new female, she may kill his nestlings by pecking them to death, so that she can mate with him and raise her own offspring. Cannibalism by siblings or parents sometimes occurs in Gray Herons. In addition, Heron and Egret families are often systematically “pared down” because the youngest nestlings starve to death when they are unable to compete for food; more than three-quarters of all nestling deaths in Little Blue Herons are the result of such “brood reduction.”
Blaker, D. (1969) “Behavior of the Cattle Egret
*Fujioka, M. (1996) Personal communication.
———(1989) “Mate and Nestling Desertion in Colonial Little Egrets.”
*———(1988) “Extrapair Copulations in Little Egrets (
———(1986a) “Infanticide by a Male Parent and by a New Female Mate in Colonial Egrets.”
———(1986b) “Two Cases of Bigyny in the Cattle Egret
———(1985) “Sibling Competition and Siblicide in Asynchronously-Hatching Broods of the Cattle Egret
*Fujioka, M., and S. Yamagishi (1981) “Extramarital and Pair Copulations in the Cattle Egret.”
Lancaster, D. A. (1970) “Breeding Behavior of the Cattle Egret in Colombia.”
McKilligan, N. G. (1990) “Promiscuity in the Cattle Egret (
*Meanley, B. (1955) “A Nesting Study of the Little Blue Heron in Eastern Arkansas.”
Milstein, P. le S., I. Prestt, and A. A. Bell (1970) “The Breeding Cycle of the Gray Heron.”
*Ramo, C. (1993) “Extra-Pair Copulations of Gray Herons Nesting at High Densities.”
Rodgers, J. A., Jr. (1980a) “Little Blue Heron Breeding Behavior.”
———(1980b) “Breeding Ecology of the Little Blue Heron on the West Coast of Florida.”
Rodgers, J. A., Jr., and H. T. Smith (1995) “Little Blue Heron (
Telfair, R. C., II (1994) “Cattle Egret (
*Werschkul, D. F. (1982) “Nesting Ecology of the Little Blue Heron: Promiscuous Behavior.”
———(1979) “Nestling Mortality and the Adaptive Significance of Early Locomotion in the Little Blue Heron.”
PUKEKO
IDENTIFICATION: A large (nearly 20 inch) wading bird with bluish purple plumage, a red shield on its forehead, and red feet with long toes. DISTRIBUTION: From the western Mediterranean through Middle East, eastern and southern Africa, and throughout Australasia. HABITAT: Wetlands, especially swamps and marshy areas. STUDY AREA: Shakespear Regional Park, North Island, New Zealand; subspecies
TASMANIAN NATIVE HEN
IDENTIFICATION: Similar to Pukeko, but flightless, and with grayish brown plumage, no red frontal shield, and shorter legs. DISTRIBUTION: Tasmania. HABITAT: Pasture, marshes, lakes, rivers. STUDY AREA: Hunting Ground, near Hobart, Tasmania.
DUSKY MOORHEN
IDENTIFICATION: Similar to Pukeko, but with black plumage and shorter legs. DISTRIBUTION: Australia, New Guinea, Indonesia. HABITAT: Wetlands. STUDY AREAS: Sullivan’s Creek and Gungahlin, near
