In: Phyton, 52 Fasc. 1 (2012), S. 121-138, with 2 figures

Key words: Ornithophily, hummingbirds, floral nectar amount, sugar concentration, energy supply. – Tropical montane forest. – Flora of Ecuador, Podocarpus National Park.

Summary

PAULSCH C., STEVENS A.-D. & GOTTSBERGER G. 2012. Dynamics of nectar resources of hum-mingbird-visited plants in a montane forest of southern Ecuador – Phyton (Horn, Austria) 52 (1): 121–138, with 2 figures.

Changes of nectar resources offered by hummingbird-visited plants in the eastern Andes of southern Ecuador were studied in an area of 1 hectare over the course of a full year. A total of 3186 flowering plant individuals were visited by hummingbirds, belonging to 67 species, 29 genera and 12 families. The mean nectar volume per flower and day was 38.6 µl with a high interspecific vari-ability (SD 153.5 µl) [calculated without the bat blossoms of Ceiba: 20.2 µl (SD 30.2 *l)]. Nectar sugars revealed an average concentration of 18.8% (SD 4.4%), with a preponderance of sucrose in a subset of species analysed by HPLC. This supports that the majority of the investigated plant spe-cies is in fact ornithophilous and regularly pollinated by hummingbirds. Short-term changes in the quantity and composition of the nectar resources were characteristic for the observed dynamics. Considered in terms of energy available, resource levels attained their maximum in a rainy month (April) and were at a minimum in a drier month (January). However, it was not possible to show significant correlations between measured precipitation and either the number of flowers or the amount of energy available. Only 27 of the 67 hummingbird-visited plant species could be verified to contribute substantially to the nectar resources; these species either flowered at least during one third of the year (contributing less than 10% of energy/day), or they contributed at least at one ob-servation date more than 10% of the total energy available. The present study substantiated that the supply of resources provided by hummingbird-visited plants in the montane rainforests of Ecuador is subject to a high degree of temporal and spatial dynamics.