Female Territoriality in the Purple-Throated Carib

Abstract

THE potential kinds of competitive interactions among individuals, regardless of species, can be classified as contest and scramble (Nicholson 1957) or interference and exploitation (Miller 1967). The two sets of terms refer to approximately equivalent phenomena. Presumably the type of competition an individual displays depends in large part on the characteristics of the limited resource (McNaughton and Wolf 1973). A resource that can be defended advantageously, in the evolutionary sense, will result in selection for contest or interference competition. One possible behavioral outcome of contest competition is territoriality, the restriction of use of a potentially limited resource in a spatially fixed area to meet the biological requirements of the individual that defends the resource (Pitelka 1959, Rand 1967, Wolf 1969). Territoriality might be expected to evolve among all classes of individuals in a species for which the cost of defending the resource does not exceed the gain achieved by the defense (Brown 1964, Cody 1974). For hummingbirds, a potentially limited resource is nectar they use as an energy source. Theoretically most individual hummingbirds might be expected to exhibit territorial behavior under appropriate conditions of nectar availability and competitor pressure (Wolf et al. 1975, Gill and Wolf 1975). The literature contains numerous reports of territoriality of male hummingbirds, but reports of female territoriality except around nests (Legg and Pitelka 1956, Wolf and Wolf 1971, Stiles 1973) or on migration (Armitage 1955, Cody 1968) are very limited (Wolf 1969). In Panterpe insignis, the Fiery-throated Hummingbird, I reported that female territoriality during the nonbreeding season in a nonmigratory species was correlated with brightly monomorphic plumage coloration and similarities in bill length between the sexes (Wolf 1969). To establish if these correlations held for other species of hummingbirds I studied the Purple-throated Carib, Eulampis jugularis, during the breeding and nonbreeding seasons on the island of Dominica, British West Indies. I also made incidental observations on the Green-throated Carib, Sericotes holosericeus. I found that both species, which are sexually monomorphic in color, are territorial around certain flower species and that females of both species hold territories during the nonbreeding season. The relationships of the sexes and of the territories held were somewhat different than