*Huber, R., and M. Martys (1993) “Male-Male Pairs in Greylag Geese (Anser anser).” Journal für Ornithologie 134:155-64.
*Lorenz, K. (1991) Here Am I—Where Are You? The Behavior of the Greylag Goose. New York: Harcourt Brace Jovanovich.
*———(1979) The Year of the Greylag Goose. New York: Harcourt Brace Jovanovich.
Olsson, H. (1978) “Probable Polygamy in the Greylag Goose, Anser anser, and an Instance of Combined Broods.” Vår Fågelvårld 37:257–58.
*Schönfeld, M. (1985) “Beitrag zur Biologie der Schwane: ‘Männchenpaar’ zwischen Graugans und Hock-erschwan [Contribution to the Biology of Swans: ‘Male Pairing’ Between a Greylag Goose and a Mute Swan].” Der Falke 32:208.
CANADA GOOSE
IDENTIFICATION: A brown-plumaged goose with a distinctive black neck and white cheek patch; varies widely in size, from 2–24 pounds. DISTRIBUTION: Mostly throughout North Amerca. HABITAT: Lakes, rivers, marshes, meadows, and tundra. STUDY AREAS: Horicon Marsh Wildlife Refuge, Wisconsin; Holkham Park, England; in captivity in Ithaca, New York; subspecies B.c. interior, the Hudson Bay Canada Goose, and B.c. canadensis, the Atlantic Canada Goose.
SNOW GOOSE
IDENTIFICATION: A pinkish-red-billed goose with two major color phases: all-white and “blue” (grayish plumage with a white head and neck). DISTRIBUTION: Alaska and north-central Canada, northwestern Greenland; winters in southern United States and northern Mexico. HABITAT: Tundra, marshes, floodlands. STUDY AREAS: La Pérouse Bay, Churchill, Manitoba, Canada; Carver Park, Minnesota; subspecies A.c. caerulescens, the Lesser Snow Goose.
Social Organization
Snow Geese are extremely gregarious and nest in dense colonies that can number in the thousands of birds; Canada Goose breeding grounds are generally less dense. In both species, birds usually pair in long-term, monogamous bonds (albeit with a number of variations—see below), and outside of the mating season they gather in large flocks.
Description:
Behavioral Expression: In Canada Geese, two birds of the same sex sometimes form a pair-bond. Both male and female homosexual pairs occur, and the partners may be either adults or juveniles; homosexual pair-bonds often persist for many years (as do heterosexual ones). Courtship behavior in the form of HEAD-DIPPING is frequently a part of such bonds: in this display, one bird ritually splashes water over the back of its head and neck by dipping its head deep into the water and then lifting it back up. In heterosexual contexts, this is often a prelude to copulation, but homosexual copulation is not a prominent feature of same-sex pairs. One exception involves trios: occasionally a bond forms between three birds—two females and one male—and sometimes one of the females will mount and copulate with the other female. Some lesbian pairs try to raise a family: one female in a homosexual pair, for example, built a nest and laid eggs while her partner stood guard, then the other female built her own nest next to the first and also laid eggs. None of the eggs hatched, however, because the females constantly rolled the eggs (which were probably not fertile in any case) back and forth between their nests and broke all of them.
Courtship between a pair of female Canada Geese: the “head-dipping” display
More successful lesbian parenting occurs in Snow Geese. Pair-bonds between females are strong: when one member of the pair is absent from her mate, the other begins loudly calling to her until she returns. The pair builds a single nest in which each female lays eggs; as a result, such nests may have SUPERNORMAL CLUTCHES containing double the number of eggs found in heterosexual nests (8 eggs versus 4–5). Both birds take turns incubating the eggs (in heterosexual pairs, the male does not incubate). Since one or both females sometimes copulate with males, some of their eggs may be fertile. When they hatch, both females raise the goslings, including defending them against intruders and predators (such as Herring Gulls) by standing over them with cupped wings. Male homosexual pairs are not found in Snow Geese, although occasionally a cross-species pairing does develop between a male Snow Goose and a male Canada Goose. The two birds become constant companions, following one another and roosting close together, although nest-building and copulation do not usually take place. However, same-sex mounting does sometimes occur between male Snow Geese who take part in heterosexual “gang rapes.” In this species, males often sexually harass females, chasing them and forcing them to copulate. In some cases, other males gather together in large “spectator” groups—sometimes containing as many as 20–80 males—to watch and perhaps even join in. Occasionally, one male mounts another male as part of the group sexual activity that ensues.
Frequency: In Canada Geese, up to 12 percent of pairs in some (semiwild) populations are homosexual. The proportion is much smaller in Snow Geese: about 1 in 200 nests belongs to a pair of females. Approximately 4 percent of all mountings during Snow Goose rape attempts are between males.
Orientation: In one study of Canada Geese, 18 percent of the males formed homosexual pair-bonds while 6–12 percent of females did. Some birds in same-sex pairs appear to “prefer” their homosexual association, even if they have the opportunity for heterosexual interactions. In one case, a male harassed a female who was part of a long-lasting lesbian pair and separated her from her companion, mating with her. However, the next year she returned to her female partner and their pair-bond resumed. On the other hand, some birds have a preference for heterosexual pairings: many males remain unpaired if there are no available females rather than forming homosexual pair-bonds with each other. In Snow Geese, females in homosexual pairs may be functionally bisexual—they sometimes copulate with up to three different males to fertilize their eggs—although their same-sex pair-bond remains primary. Males who mount other males are otherwise primarily heterosexual, since most are paired with females and the majority of their sexual interactions are probably not with males.
Nonreproductive and Alternative Heterosexualities
As mentioned above, heterosexual rape is common in Snow Geese: during some mating seasons, each female is subjected to a rape attempt every five days (on average). Females are occasionally successful in thwarting such attacks, but males who rape can be very aggressive and may attack in groups. Sometimes the female’s mate can successfully chase an intruder off, but often he is not around to defend her because he is also raping another female. Significantly, most rapes are nonreproductive: more than 80 percent of all rape attempts are directed toward females that are nonfertilizable, such as incubating birds, and only about 2 percent of goslings are actually fathered this way. Rape is much less common among Canada Geese. However, ganders frequently harass and attack neighboring females when their mates are gone, often leading to abandonment of their eggs—as many as one-quarter of all nests may end up being deserted this way.
Several other variations on the heterosexual nuclear family occur in these species. Although most male-female pairs remain together for life, divorce and remating do occasionally take place in both Canada and Snow Geese. In addition, although most Snow Goose families remain together until the next breeding season, in some populations as many as 20 percent of the families split or break up before that time, usually because of separation of juveniles. Polygamous, heterosexual trios consisting of one male and two females sometimes form in Canada Geese (these differ from the bisexual trios described above in that the females are not bonded to each other). Some birds pair outside of their species, and Snow and Canada Geese may in fact mate with each other. CRÈCHES or combined broods—containing as many as 60 young—are sometimes found in Canada Geese, attended by one or several heterosexual pairs. In addition, families often “trade” goslings, caring for young other than their own on either a temporary or permanent basis. Up to 46 percent of Canada Goose broods and at least 13 percent of Snow Goose broods may contain adopted young, and over 60 percent of Canada broods in some populations experience a loss and/or gain of goslings due to adoption. Egg “adoption” is also common in Snow Geese because females often lay eggs in nests other than their own: 15–22 percent of all nests contain such eggs (although in some colonies more than 80 percent of nests may be affected), and more than 5 percent of all goslings are raised by a female other than their biological mother. Females that lay eggs in others’ nests are often aided by their mates, who 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.