AN ASSEMBLAGE OF HUMMINGBIRD-POLLINATED FLOWERS IN A MONTANE FOREST IN SOUTHEASTERN BRAZIL

Relationships between ornithophilous flowers and hummingbirds have bee n little studied in southern South America, where hummingbird species richness is low. We studied an ornithophilous flower assemblage and th e hummingbird pollinators in a montane forest in southeastern Brazil. Twenty-three native hummingbird-pollinated plant species in 21 genera and 14 families were observed. Bromeliaceae, Fabaceae, Gesneriaceae, a nd Lobeliaceae are represented by more than one species within the ass emblage. Flower shapes vary from narrow tube to bowl-shape, but tubula r flowers prevail. The variety of flower shapes and sizes results in d iverse pollen placement on the body parts of hummingbird visitors, alt hough pollen is deposited mostly on the bill. Sugar concentration in n ectar averages 22.1%, and nectar volume per flower averages 16.9 mu l. The plant populations bloom for one month to year-round, and their fl owering approaches the steady-state pattern. Four flower subsets may b e defined within the assemblage, each subset related to the bill size and foraging habits of the most frequent bird visitor. Of the six spec ies of humming-birds recorded at the study site, four are common and l argely resident. The four hummingbirds differ in bill size, body mass, and favoured foraging sites, attributes which reflect their favoured flower subsets. One hermit and one trochiline hummingbird share most o f the flower species they use, these two birds being the major pollina tors within the flower assemblage. This montane forest community may b e viewed as medium-rich in ornithophilous flower species and poor in h ummingbird species.