Diglossa

Abstract: In the highlands of southern Costa Rica, one of the commonest native plants of second-growth areas is Centropogon vu&i Standl. ( Lobeliaceae), a perennial shrub with orange-red tubular flowers (Wilbur 1972). Although some flowers are produced by C. vu&i in all months of the year, in the dry season (December through March) a single plant may have over a hundred open flowers on a continual basis. During this flowering peak, most large clumps of C. vale&i are pollinated primarily by the Green Violet-ear ( Co&i thalussinus cubunidis) (Trochilidae). This hummingbird is an altitudinal migrant, spending the rest of the year at lower elevations (Skutch 1967; Slud 1965; see also Wagner 1945; Wolf and Stiles 1970). In the highlands, the male violet-ear often sets up a territory around patches of C. u&r%, which he defends vigorously against others of his own species, as well as hummingbirds of other species (Colwell 1973; Wolf 1969; Wolf and Stiles 1970). In what must be among the earliest descriptions of territoriality in hummingbirds, Boucard (1878) said of this species: “They take possession of a certain space containing several of these shrubs [very likely Centropogonl; and when not feeding on these flowers, they perch on a dry branch near the place, and fight all the other Humming-birds that dare to intrude.” Besides other hummingbirds, the Green Violet-ear has two additional potential competitors for the nectar of C. vuletii, both of them nonpollinating nectar thieves. The Slaty Flower-piercer (Diglossu plumbea) (“Coerebidae”) punctures the base of the corolla with its lower mandible and extracts nectar with its tongue, often while perching on the pedicel (in C.