while those males who approach displaying males are most likely nondrumming “alternate” males (see below) that do not mate heterosexually.
Nonreproductive and Alternative Heterosexualities
In both of these species, significant portions of the population are nonbreeding. As many as 30 percent of male Ruffed Grouse are nondrummers who do not mate heterosexually, and some birds never breed during their entire lives. In fact, one researcher found that nonbreeders live longer and have a better survival rate than breeders. Many nonbreeders are younger males who have yet to acquire a drumming log; others are ALTERNATE males that tend to associate with another male on his display site without themselves drumming. Still others give up or “abdicate” their display territories and become nonbreeders. Up to 25 percent of female Ruffed Grouse may not nest in any given year, as is true for 20-32 percent of female Sage Grouse in some populations. Moreover, 14-16 percent of female Sage Grouse abandon their nests (especially if they have been disturbed), which means that any eggs or chicks they have will not survive; this also occasionally occurs in Ruffed Grouse. The majority of Sage Grouse copulations are performed by only a small fraction of the male population, and one-half to two-thirds of males never mate at all; during each breeding season, 3-6 percent of females do not ovulate either.
Even among birds that do mate, heterosexual copulation is often complicated by a host of factors: female Sage Grouse may refuse to be mounted, males often ignore females’ solicitations to mate (especially later in the breeding season), and 10–18 percent of copulations are disrupted by neighboring males who attack mating birds. In addition, males and females are often physically separated from each other: in both species, typically the only contact the two sexes have with each other during the breeding season is mating. Since each female usually copulates only once, hers is a largely male-free existence. Even on the display grounds, Sage Grouse are typically sex-segregated when not actually mating. Several types of alternative sexual behavior also occur in these species. Male Sage Grouse often “masturbate” by mounting a pile of dirt or a dunghill and performing all the motions of a full copulation. Both male Ruffed and Sage Grouse occasionally court and mate with females of other grouse species. And male Sage Grouse sometimes mount females without attempting to inseminate them (no genital contact). Moreover, even though most females mate only once (that is, the minimum required to fertilize their eggs), multiple copulations also occasionally occur: one female, for example, was mounted more than 22 times in one hour. Female Sage Grouse sometimes combine their youngsters into what is known as a GANG BROOD, a communal “nursery flock” of sorts.
Other Species
Homosexual activity occurs in several species of pigeons. Feral Rock Doves (
*Allen, A. A. (1934) “Sex Rhythm in the Ruffed Grouse (
*Allen, T. O., and C. J. Erickson (1982) “Social Aspects of the Termination of Incubation Behavior in the Ring Dove (
Bergerud, A. T., and M. W. Gratson (1988) “Survival and Breeding Strategies of Grouse.” In A. T. Bergerud and M. W. Gratson, eds.,
*Brackbill, H. (1941) “Possible Homosexual Mating of the Rock Dove.”
*Gibson, R. M., and J. W. Bradbury (1986) “Male and Female Mating Strategies on Sage Grouse Leks.” In D. 1. Rubenstein and R. W. Wrangham, eds.,
Gullion, G. W. (1981) “Non-Drumming Males in a Ruffed Grouse Population.”
———(1967) “Selection and Use of Drumming Sites by Male Ruffed Grouse.”
Hartzler, J. E. (1972) “An Analysis of Sage Grouse Lek Behavior.” Ph.D. thesis, University of Montana.
Hartzler, J. E., and D. A. Jenni (1988) “Mate Choice by Female Sage Grouse.” In A. T. Bergerud and M. W. Gratson, eds.,
Johnsgard, P. A. (1989) “Courtship and Mating.” In S. Atwater and J. Schnell, eds.,
*Johnston, R. F., and M. Janiga (1995)
Lumsden, H. G. (1968) “The Displays of the Sage Grouse.”
*Patterson, R. L. (1952)
Schroeder, M. A. (1997) “Unusually High Reproductive Effort by Sage Grouse in a Fragmented Habitat in North-Central Washington.”
*Scott, J. W. (1942) “Mating Behavior of the Sage Grouse.”
Simon, J. R. (1940) “Mating Performance of the Sage Grouse.”
Wallestad, R. (1975)
*Wiley, R. H. (1973) “Territoriality and Non-Random Mating in Sage Grouse,
HUMMINGBIRDS, WOODPECKERS, AND OTHERS
LONG-TAILED HERMIT HUMMINGBIRD
IDENTIFICATION: A medium-sized hummingbird with purplish or greenish bronze upperparts, a striped face, a long, downward-curving bill, and elongated tail feathers. DISTRIBUTION: Southwestern Mexico, Central America, northwestern South America. HABITAT: Tropical forest undergrowth. STUDY AREA: La Selva Biological Reserve, Sarapiqui, Costa Rica.
ANNA’S HUMMINGBIRD
IDENTIFICATION: A medium-sized hummingbird (up to 4 inches long) with an iridescent, rose- colored throat and crown (in males), and a bronze-green back. DISTRIBUTION: Western United States to northwestern Mexico. HABITAT: Woodland, chaparral, scrub, meadows. STUDY AREA: Franklin Canyon, Santa Monica Mountains, California.
Social Organization
Long-tailed Hermit Hummingbirds form singing assemblies or LEKS composed of about a dozen males and have a polygamous or promiscuous mating system (in which birds mate with multiple partners). Anna’s Hummingbirds are not particularly social: each bird defends its own territory and does not generally associate with others. No pair formation occurs as part of the mating system; instead, males and probably also females mate with several different partners.
Description
Behavioral Expression: Male Long-tailed Hermit Hummingbirds gather on their leks or courtship display territories in dense, stream-side thickets, singing to advertise their presence and attract birds to mate with. Their
