Nutrients in fruits as determinants of resource tracking by birds

BLENDINGER, PG; GIANNINI, NP; ZAMPINI, I.C.; ORDOÑEZ, R.; TORRES, S.; SAYAGO, J.E.; RUGGERA, R.A.; ISLA, M.I.

IBIS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2015

0019-1019

Fruit pulp is an important source of nutrients for many bird species world-wide. Fruit-eating birds use a variety of strategies to cope with changes in the availability of fruits, exhibiting a remarkable ability to track resources. In this study, we assessed the role of nutrient availability in the fruiting environment as a factor driving resource tracking by fruit-eating birds. We studied fruit consumption by the four most common frugivorous species in a 6 ha plot located in the Southern Yungas montane forest of Argentina. We determined content of selected nutrients (soluble carbohydrates, proteins, phenols, ascorbic acid, and essential minerals) in 22 consumed fruiting species, and during two years we measured fruit-frugivore interactions and availability of nutrients and dry pulp mass. We found a strong covariation in availability of nutrients in fruits per unit area across the study period. Similarly, availability of nutrients in the fruiting environment covaried with pulp mass availability. Fruit consumption by the four species, and bird abundance of most species, were positively associated to nutrient availability and to dry pulp mass availability. Nutrient availability was a good predictor of temporal fruit tracking by three of the four fruit-eating bird species. In spite of large differences in particular nutrient concentrations in fruits, overall nutrient (and pulp) quantity in the fruiting environment played a major role in fruit tracking as compared with nutritional reward (an expression of the nutritional quality of fruits) offered in fruits. While the overall nutrient availability (i.e., across fruit) and pulp mass were important determinants of fruit tracking, we propose that species-specific differences in fruit nutrient concentration may be important mainly in short-term foraging decisions involved in fruit choices and nutritional balance.