Female Territoriality in a Tropical Hummingbird

Abstract

THE latest summary of territoriality in hummingbirds (Pitelka, 1942) reports that females of some species defend a spatially circumscribed area during the breeding season. The available data suggest that defense is limited to an area surrounding the nest site, with the possible inclusion of certain feeding areas near the nest. Females of a few species may hold temporally and spatially limited territories around localized feeding sites during and after the breeding season. Several recent studies refer to females defending a nest area (Dorst, 1962) or birds on migration defending a small area in a locally common food source (Armitage, 1955; Cody, 1968). Recent studies in arid tropical lowlands in Costa Rica suggest that females of several resident species hold nonbreeding territories similar to those of the males (Stiles and Wolf, 1969). The present study documents female territoriality in a highland tropical hummingbird, Panterpe insignis, during the nonbreeding season. (Unfortunately nothing is known of the territorial system in this species during the breeding s.eason.) This report also suggests possible ecologic factors that produce selective pressures for female territoriality and some possible morphological and behavioral consequences of this territorial social system in hummingbirds. The Fiery-throated Hummingbird, Panterpe insignis, the only member of its genus, is distributed throughout high montane central and southern Costa Rica and western Panama (Slud, 1964) where it is limited almost entirely to elevations above 2,000 meters. The primary habitat is clearings where secondary succession has reached the shrubby stage. The birds also enter partly cleared forests where epiphytes (Bromeliaceae, Ericaceae, Loranthaceae) grow on the large oaks that dominate the woodlands at this elevation. More detailed accounts of the ecology and behavior of this species, especially its ecological and behavioral relations with the sympatric complex of nectar-feeding birds, are being prepared. Panterpe is a brightly colored hummingbird in which both sexes are so similarly colored that Ridgway (1911: 511 footnote) was unable to find . . . even an average difference of coloration between the sexes, some of the most brightly colored specimens being females, while some of the dullest are males.. Near the middle of the major study period (April) I was able to sex most individuals I handled in the field, and later coillected, on the basis of a slight size difference (Table 1 ) and sometimes by a difference in the degree of feather wear on the lower abdomen. The difference in wear left the lower belly of some females slightly grayer than the males.