Floral resource for birds in an Atlantic montane raiforest site : seasonality and vertical distribution / Recurso floral para aves em uma comunidade de Mata Atlantica de encosta : sazonalidade e distribuição vertical

AUTOR(ES)

Marcia Alexandra Rocca-de-Andrade

DATA DE PUBLICAÇÃO

2006

RESUMO

Hummingbirds are considered the most important vertebrate pollinators in the Neotropics. Other flowervisiting birds are often considered as parasites of the flower-hummingbird relationship, not presenting the high degree of specialization for nectarivory as hummingbirds. Although ornithophilous flowers are very showy, displaying colorful floral parts or structures associated with the flowers or inflorescences, hummingbirds also visit non-ornithophilous flowers, which most of the time are not pollinated during nectar probing. In a two years and three months study about floral resource availability for birds in the Atlantic rainforest in South-eastern Brazil, their activities and flower abundance were estimated throughout the studied months and in vertical stratification. Records were made every month, during line transects samplings and accessing canopy with climbing equipment. Accumulated nectar volume and concentration were measured with microliter syringes and a hand-refractometer, respectively, from bagged flowers at the end of the morning. Bird species were registered during sightings and focal observations while visits to flowers. Sixtytwo species of plants were studied and hummingbirds were recorded on 95% of them; a few were also visited by other birds. Most species are epiphytes, and some are shrubs, lianas or trees. About 68% of these species are pollinated by hummingbirds, from the others they steal or rob nectar. Flowers visited by hummingbirds are distributed throughout the year, which is important to support resident species, and most of this resource occurs in the understorey, although there is also resource in the canopy. Nectar features are very variable among species: mean accumulated nectar volume ranging from 1.5 to 220.6 µl, and mean sugar concentration from 3.1 to 40.9% (Chapter 1). Among the hummingbirds, three species belong to the subfamily Phaethornithinae and ten to Trochilinae. Two resident species are recorded all over the vertical stratification, visiting flower species along their vertical distribution, carrying pollen between different strata, while other species only occur in one stratum: understorey or canopy (Chapter 2). In the canopy two species are visited and pollinated by other birds besides hummingbirds, even by woodpeckers (Chapter 3.1), and are more adapted to pollination by perching-birds (Chapter 3.2). One of the bromeliads (Vriesea rodigasiana) was chosen for a study about relative pollinator efficiency, measured by visitation frequency and germinated pollen load per visit (Chapter 3.3)

ASSUNTO(S)

nectar plants picideo passeriformes beija-flor dossel dossel passaro plantas meliferas picidae trochilidae

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