Trophic ecology of the Ringed Warbling-Finch (Poospiza torquata) in Neotropical semi-arid scrublands

Abstract

Seed-eating birds in temperate deserts must cope with great variation in the availability of their food resources. We studied the trophic ecology of Ringed Warbling-Finches (Poospiza torquata) in semi-arid scrublands of the Monte Desert, Argentina. We assessed seasonality in the availability of seed and in the consumption of arthropods and seeds at a regional scale, and evaluated the composition of the granivorous component of the diet and the seed dietary breadth. Ringed Warbling-Finches had a granivorous–insectivorous diet consistinglargely of arthropods in summer and seeds and arthropods in winter. The granivorous component of the diet consisted mainly of grass seeds, but with low breadth of the winter seed diet. To deal with seasonal variation in the availability of food resources, Ringed Warbling-Finches switched opportunistically between different resources, exploiting alternating seasonal patterns of food abundance. This seasonal switching is a wellestablished strategy in the behaviour of the species and was observed in all Ringed Warbling-Finch populations studied across the Monte Desert. Our results show the flexibility of foraging strategies of Ringed Warbling-Finches, an opportunist species that adjusts their relative consumption of seeds and arthropods in response to the spatial and temporal variations in these food resources.