Bruce Bagemihl - Biological Exuberance

Heterosexual pairs in Ring-billed and Common Gulls exhibit a variety of bonding and parenting arrangements (like homosexual pairs). Not all males and females couple for life: the heterosexual divorce rate is about 28 percent in both species. Polygamous heterosexual trios—two females bonded to the same male, but not to each other—are also found in both species, as are occasionally even quartets (three females with one male). Common Gull pairs sometimes foster-parent chicks, while another form of “adoption” occurs in these species when females occasionally lay eggs in nests belonging to other pairs or roll eggs from other nests into their own. Moreover, because of parental ineptitude or inefficiency (such as poor feeding), at least 8 percent of Ring-billed chicks abandon or “run away” from their own families; most of these are adopted and cared for by other families.

About 4 percent of Ring-billed pairs continue to engage in courtship and copulation after the hatching of their eggs—when sexual activity is not directly reproductive—and about 5 percent of adults court and mount chicks. Most of this activity involves females behaving incestuously with their own offspring, including full copulatory REVERSE mounts of young birds. Mounted chicks may be as young as two weeks old, and they usually collapse under the weight of the adult mounting them and cry out in distress. Some individuals appear to be “habitual molesters” in that they repeatedly interact sexually with chicks, including their own. In addition to sexual molestation, Ring-billed chicks are often subjected to vicious attacks from neighboring adults when their parents are away, or if they stray outside of their home territory. About 1 in 300 chicks is killed by such assaults, and infanticide can account for between 5 percent and 80 percent of all chick deaths (depending on the population).

Female pairs that lay supernormal clutches also occur in California Gulls (Larus californicus ), where they constitute about 1 percent of all pairs.

*asterisked references discuss homosexuality/transgender

Brown, K. M., M. Woulfe, and R. D. Morris (1995) “Patterns of Adoption in Ring-billed Gulls: Who Is Really Winning the Inter-generational Conflict?” Animal Behavior 49:321—31.

*Conover, M. R. (1989) “Parental Care by Male-Female and Female-Female Pairs of Ring-billed Gulls.” Colonial Waterbirds 12:148—51.

*———(1984a) “Frequency, Spatial Distribution, and Nest Attendants of Supernormal Clutches in Ring-billed and California Gulls.” Condor 86:467-71.

*———(1984b) “Consequences of Mate Loss to Incubating Ring-billed and California Gulls.” Wilson Bulletin 96:714—16.

*———(1984c) “Occurrence of Supernormal Clutches in the Laridae.” Wilson Bulletin 96:249-67.

*Conover, M. R., and D. E. Aylor (1985) “A Mathematical Model to Estimate the Frequency of Female-Female or Other Multi-Female Associations in a Population.” Journal of Field Ornithology 56:125-30.

*Conover, M. R., and G. L. Hunt, Jr. (1984a) “Female-Female Pairings and Sex Ratios in Gulls: A Historical Perspective.” Wilson Bulletin 96:619—25.

*———(1984b) “Experimental Evidence That Female-Female Pairs in Gulls Result From a Shortage of Males.” Condor 86:472—76.

*Conover, M. R., D.E. Miller, and G. L. Hunt, Jr. (1979) “Female-Female Pairs and Other Unusual Reproductive Associations in Ring-billed and California Gulls.” Auk 96:6—9.

Emlen, J. R., Jr. (1956) “Juvenile Mortality in a Ring-billed Gull Colony.” Wilson Bulletin 68:232—38.

Fetterolf, P. M. (1983) “Infanticide and Non-Fatal Attacks on Chicks by Ring-billed Gulls.” Animal Behavior 31:1018—28.

———(1984) “Ring-billed Gulls Display Sexually Toward Offspring and Mates During Post-Hatching.” Wilson Bulletin 96:12—19.

*Fetterolf, P. M., and H. Blokpoel (1984) “An Assessment of Possible Intraspecific Brood Parasitism in Ring-billed Gulls.” Canadian Journal of Zoology 62:1680—84.

*Fetterolf, P. M., P. Mineau, H. Blokpoel, and G. Tessier (1984) “Incidence, Clustering, and Egg Fertility of Larger Than Normal Clutches in Great Lakes Ring-billed Gulls.” Journal of Field Ornithology 55:81—88.

*Fox, G. A., and D. Boersma (1983) “Characteristics of Supernormal Ring-billed Gull Clutches and Their Attending Adults.” Wilson Bulletin 95:552—59.

Kinkel, L. K., and W. E. Southern (1978) “Adult Female Ring-billed Gulls Sexually Molest Juveniles.” Bird-Banding 49:184—86.

*Kovacs, K. M., and J. P. Ryder (1985) “Morphology and Physiology of Female-Female Pair Members.” Auk 102:874—78.

*———(1983) “Reproductive Performance of Female-Female Pairs and Polygynous Trios of Ring-billed Gulls.” Auk 100:658—69.

*———(1981) “Nest-site Tenacity and Mate Fidelity in Female-Female Pairs of Ring-billed Gulls.” Auk 98:625—27.

*Lagrenade, M., and P. Mousseau (1983) “Female-Female Pairs and Polygynous Associations in a Quebec Ring-billed Gull Colony.” Auk 100:210—12.

Nethersole-Thompson, C., and D. Nethersole-Thompson (1942) “Bigamy in the Common Gull.” British Birds 36:98—100.

*Riddiford, N. (1995) “Two Common Gulls Sharing a Nest.” British Birds 88:112—13.

*Ryder, J. P. (1993) “Ring-billed Gull.” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century , no. 33. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists Union.

*Ryder, J. P., and P. L. Somppi (1979) “Female-Female Pairing in Ring-billed Gulls.” Auk 96:1—5.

Southern, L. K., and W. E. Southern (1982) “Mate Fidelity in Ring-billed Gulls.” Journal of Field Ornithology 53:170—71.

Trubridge, M. (1980) “Common Gull Rolling Eggs from Adjacent Nest into Own.” British Birds 73:222—23.

IDENTIFICATION: A large gull (up to 27 inches) with a dark gray back and wings; spotted black-and-white wing tips; pink legs; and a yellow bill with a red spot. DISTRIBUTION: Pacific coast of North America. HABITAT: Cliffs, rocky seacoasts, bays. STUDY AREAS: Santa Barbara Island and other Channel Islands, California; subspecies L.o. wymani.

IDENTIFICATION: A smaller gull (to 17 inches) with a blue-gray mantle; more pointed black wing tips; relatively short black legs and dark eyes; and a yellowish green bill. DISTRIBUTION: Northern Pacific and Atlantic Oceans; adjacent Arctic Ocean. HABITAT: Oceangoing; breeds on coasts. STUDY AREA: North Shields, Tyne and Wear, England; subspecies R.t. tridactyla .

Western Gulls and Kittiwakes form pair-bonds and nest in colonies, some of which contain upwards of 10,000 pairs; Kittiwakes often nest on cliffs. Outside of the breeding season they are less sociable, occasionally gathering in loose aggregations when not solitary.

Behavioral Expression: Female Western Gulls sometimes form homosexual pairs, as do Kittiwakes. In Western Gulls, the females participate in courtship, sexual, and parenting behaviors similar to those of heterosexual pairs in their basic patterns, yet different in many details. Two females court one another by performing HEAD-TOSSING (a stylized bobbing of the head with the bill pointed skyward) and COURTSHIP-FEEDING (in which a small amount of food is regurgitated and offered as a “gift” to the partner). In heterosexual pairs, males usually perform more courtship-feeding and females more head-tossing. In homosexual pairs, both birds perform these behaviors—often with equal frequency—although the overall rate of courtship behaviors for each female is similar to females in heterosexual pairs. Homosexual courtship-feeding differs from the heterosexual pattern in that a female does not offer as large an amount of food to her female partner and may even swallow the “offering” herself rather than give it to her mate. In some female pairs, one partner regularly mounts the other and may even utter the copulation call characteristic of heterosexual matings. Some females adopt unique mounting positions such as sideways or head-to-tail (not seen in heterosexual matings), and genital contact does not usually occur. Like heterosexual pairs, female couples establish territories that they defend against intruders. Both females spend a great deal of time on their territories (typical only of females in heterosexual pairs), while both also exhibit aggressive reactions to intruders (more typical of males in heterosexual pairs). Once a homosexual pair-bond is established, it usually persists for many years, and the two females return to the same territory each season: one study that tracked eight homosexual pairs found that seven of them remained together for more than one breeding season.