Using stable isotopes to trace resource acquisition and trophic position in four Afrotropical birds with different diets
Abstract
Here we test the potential of stable carbon isotopes to ascertain the relative contribution of primary carbon sources and the potential of stable nitrogen isotopes to assess the foodweb trophic level in four Afrotropical birds, each representing the following types of consumers: frugivorous (Andropadus tephrolaemus), nectarivorous (Cinnyris reichenowi), granivorous (Estrilda nonnula), and insectivorous (Cisticola chubbi). The four species largely differed in their feather isotope values.
In agreement with their known habitat preferences, stable carbon isotopes showed that the frugivore and the nectarivore relied mostly on C3 plant dietary sources, whereas both the granivore and the insectivore depended on diet originating from a higher proportion of C4 plant-based food. Stable nitrogen isotopes confirmed the expected trophic positions of the four species.
Both stable isotope tracers suggested that the granivore occupies a considerably wide isotopic niche relative to the other species