Identification: a medium-sized (to 18 inches) black-headed gull with white eye-crescents, a dark gray back, and red legs and bill..

Ivory gull

Identification: An all-white gull with black legs and a blue-gray bill.

Social Organization

Laughing Gulls are highly social and gregarious, forming large flocks at all times of the year, while Ivory Gulls tend to be more solitary or gather in smaller flocks. Their mating system involves pair-bonding, and birds nest in colonies that contain a few dozen pairs in Ivories and several hundred to as many as 25,000 pairs in Laughing Gulls.

Description

Behavioral Expression: Pair-bonds sometimes develop between two male Laughing Gulls, including sexual and parenting activities as well as unique courtship and territorial behaviors. A homosexual bond begins when two males KEEP COMPANY: in this courtship activity, they approach and circle each other while performing elegant FACING-AWAY or HEAD-TOSS displays (in which the birds ritually turn their heads in opposite directions or flick them upward from a hunched posture). This is followed by a period of resting together somewhat apart from the other Gulls. Two males may even begin courting in this way early in the breeding season before heterosexual couples have started their courtships. Male partners also COURTSHIP-FEED each other, in which they present one another with a symbolic “gift” of food. Although this behavior is also found in opposite-sex courtship, in homosexual pairs it has a unique feature. The two males pass the food back and forth between them many times before one or both of them eat it, whereas in heterosexual pairs, the male presents the food to the female, who immediately eats it. Pair-bonded males also mount each other, although genital contact usually does not occur. Mounting is generally not one-sided, although one male may prefer being mounter or mountee more than the other. In one male couple, for example, one partner mounted the other nine times over the season while the other mounted him three times. Homosexual (as well as heterosexual) mounts may be accompanied by distinctive staccato COPULATION CALLS by the mounting male, sounding like kakakakakaka. Both males in homosexual pairs build a nest together; in captivity, pairs take turns incubating eggs when these are supplied to the couple. After the eggs hatch, both males share parenting duties such as feeding and protecting the chicks and are able to successfully raise the youngsters.

Male couples can be quite aggressive, repeatedly intruding on neighboring territories of heterosexual pairs, who try, often unsuccessfully, to deter them. During these “raids,” the males may engage in sexual behavior with one another, or they may even try to court or mount a neighboring female. Similar territorial invasions are sometimes also made by single males, heterosexually paired males, or “coalitions” of two males that are not necessarily bonded or sexually involved with each other. In these cases, the intruding males often mount the male partner of the heterosexual pair they encounter, sometimes in full view of his incubating female mate (who is usually indifferent). If there are two intruding males, they may take turns in homosexual mounts on the male of the pair. The mounted male usually responds by violently shaking, pecking, and fluttering in order to dislodge the mounter—who may end up getting grabbed by the beak and tossed over his head. Sometimes an intruding male will even mount a male who is copulating with his female partner, creating a three-bird “pile-up.”

A similar sort of forced homosexual mounting occurs in Ivory Gulls. Males approach incubating birds whose partners are away from the nest. The intruding male carries a distraction “gift” of nesting material—usually a lump of moss—and circles the nest. He then suddenly jumps on the back of the incubating bird—even if it is a male—and attempts to copulate. As in Black-headed Gulls, the mounted bird usually responds violently.

Frequency: In a zoo population of Laughing Gulls, one pair-bond out of a total of four was between two males; the incidence of homosexual pairs in wild birds is not known, although homosexual mounts by intruding males have been documented in wild birds. Forced mountings on incubating Ivory Gulls are very frequent in some colonies in the wild, although it is not known specifically what proportion are same-sex.

Orientation: Male Laughing Gulls in homosexual pairs may be simultaneously bisexual, since they sometimes court and mount females while maintaining their primary same-sex pair-bond. Intruding males that participate in homosexual mounts may also be bisexual if they are paired to a female, although unpaired males engage in this activity as well. Such males also mount females during their intrusions, but in many cases they are clearly “targeting” the male partner. For example, they may completely ignore the female as she sits incubating, or they may remain mounted on the male after he dismounts from the female during a “pile-up,” again ignoring the female once she becomes “available.” Most males that are subject to intruding mounts like this probably have a primary heterosexual orientation, since they usually react aggressively to any homosexual activity. However, it must be remembered that females with a primary heterosexual bond also react violently to mounts by intruding males.

Nonreproductive and Alternative Heterosexualities

Female Laughing Gulls occasionally “adopt” and incubate eggs laid in their nests by other females, including females of other species such as clapper rails (Rallus longirostris ). Heterosexual pairs in this species also have very high copulation rates, mating as often as nine times a day prior to egg laying. As noted above, forced copulation attempts are common in Laughing and Ivory Gulls as well, and many of these are heterosexual. About 30 percent of male Laughing Gull territorial intruders attempt to rape females, although such attacks are usually thwarted by the female and her mate; in addition, most are directed toward incubating females and hence are nonreproductive. Abuse and violence by heterosexual parents against chicks also occur in both species. During raids by predators such as snowy owls (Nyctea scandiaca ), a pandemonium often develops in Ivory Gull breeding colonies, and groups of adult Gulls mob terrified chicks and sometimes even attack and kill them. The adults also puncture eggs and eat them; eggs containing fully developed embryos about to hatch are smashed and the yolk sac is eaten, but the down-covered embryo is discarded. Laughing Gulls also occasionally attack, kill, and even eat chicks (as well as eggs) on neighboring territories; cannibalism appears to be limited to a few individuals in dense colonies who repeatedly perform this behavior.

CASPIAN TERN