distract the nest-owning gander by acting as a decoy for him to attack, allowing the female to approach the nest and lay her eggs. Sometimes the intruding female actually helps with building or repairing the nest; for her part, the nest-owning female often actively adopts foreign eggs that have not been laid directly in the nest by rolling them into her own clutch.
Snow Goose females also occasionally “abandon” their eggs by laying in what are known as DUMP NESTS, which contain large numbers of unincubated eggs from many different females. Abandonment of nests may also be triggered by the stresses of reproduction: females can lose up to a third of their body mass while incubating, and some individuals desert their clutches or even starve on the nest as a result of such hardships. Most Snow Goose nesting colonies also have a nonbreeding flock on their peripheries. In some years, the proportion of nonbreeding adults is sizable—as much as 40 percent of the population—and occasionally an entire colony will forgo breeding (for example if the weather is particularly adverse). Many Canada Goose heterosexual pairs are nonbreeding as well: in some populations, for example, more than a quarter of all male-female pairs do not procreate, although they may copulate frequently. In fact, some nonbreeders have sexual activity rates that are almost twice as high as pairs that do reproduce.
*Allen, A. A. (1934) “Sex Rhythm in the Ruffed Grouse (
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*Collias, N. E., and L. R. Jahn (1959) “Social Behavior and Breeding Success in Canada Geese (
*Conover, M. R. (1989) “What Are Males Good For?”
Cooke, E, and D. S. Sulzbach (1978) “Mortality, Emigration, and Separation of Mated Snow Geese.”
Cooke, F., M. A. Bousfield, and A. Sadura (1981) “Mate Change and Reproductive Success in the Lesser Snow Goose.”
*Diamond, J. M. (1989) “Goslings of Gay Geese.”
Ewaschuk, E., and D. A. Boag (1972) “Factors Affecting Hatching Success of Densely Nesting Canada Geese.”
*Grether, G. F., and A. M. Weaver (1990) “What Are Sisters Good For?”
*Klopman, R. B. (1962) “Sexual Behavior in the Canada Goose.”
Lank, D. B., P. Mineau, R. F. Rockwell, and F. Cooke (1989) “Intraspecific Nest Parasitism and Extra-Pair Copulation in Lesser Snow Geese.”
Luekpe, K. (1984) “A Strange Goose: Canada-Snow Hybrid?”
MacInnes, C. D., R. A. Davis, R. N. Jones, B. C. Lieff, and A. J. Pakulak (1974) “Reproductive Efficiency of McConnell River Small Canada Geese.”
Martin, K., F. G. Cooch, R. F. Rockwell, and F. Cooke (1985) “Reproductive Performance in Lesser Snow Geese: Are Two Parents Essential?”
*Mineau, P., and F. Cooke (1979) “Rape in the Lesser Snow Goose.”
Nastase, A. J., and D. A. Sherry (1997) “Effect of Brood Mixing on Location and Survivorship of Juvenile Canada Geese.”
Prevett, J. P. and C. D. MacInnes (1980) “Family and Other Social Groups in Snow Geese.”
*Quinn, T. W., J. C. Davies, F. Cooke, and B. N. White (1989) “Genetic Analysis of Offspring of a Female- Female Pair in the Lesser Snow Goose (
*Starkey, E. E. (1972) “A Case of Interspecific Homosexuality in Geese.”
Syroechkovsky, E. V. (1979) “Podkladyvaniye byelymi gusyami yaits v chuzhiye gnyezda [The Laying of Eggs by White Geese into Strange Nests].”
Williams, T. D. (1994) “Adoption in a Precocial Species, the Lesser Snow Goose: Intergenerational Conflict, Altruism, or a Mutually Beneficial Strategy?”
Zicus, M. C. (1984) “Pair Separation in Canada Geese.”
BLACK SWAN
IDENTIFICATION: The only swan with fully black plumage; wing feathers are white, bill is bright red, and the neck is especially long. DISTRIBUTION: Australia, Tasmania, New Zealand. HABITAT: Lakes, lagoons, swamps, bays, floodlands. STUDY AREAS: Lake George and Lake Bathurst, New South Wales, Australia; in captivity at the Division of Wildlife Research, Canberra, Australia.
MUTE SWAN
IDENTIFICATION: A large swan (up to 33 pounds) with a black knob at the base of its reddish orange bill (less prominent in females). DISTRIBUTION: Europe and temperate Asia. HABITAT: Marshes, ponds, lakes, slow-moving rivers, lagoons, coastal areas. STUDY AREAS: Abbotsbury (Dorset) and Rainworth Lodge (Notts), England; Renfrewshire, Scotland.
Social Organization
Black Swans sometimes flock by the thousands and usually form mated pairs (although with numerous variations—see below) that nest either colonially or in separate territories. Mute Swans also generally develop long-term, monogamous bonds and nest in widely spaced territories, although some pairs form nesting colonies. Outside of the breeding season, they often associate in flocks.
Description
Male pairs of Black Swans fiercely defend territories that, during the mating season, are often significantly larger than those of heterosexual pairs. Because two males are able to pool their strength, they are more successful at chasing away other swans and can often annex a major portion of a pond (1,500–3,300 square feet) into their territory. In contrast, heterosexual pairs are often relegated to less favorable nesting areas and smaller territories (15–60 square feet). Homosexual pairs are also successful parents, acquiring nests and eggs in two different ways. Some male pairs associate temporarily with a female, building a nest together, mating with her, and