Diet of Cocoi Heron (Ardea cocoi) in the Flood Valley of the Paraná River

Abstract

We analysed the feeding ecology of Ardea cocoi based on twenty nine individuals captured on the Carabajal island (Santa Fe, 31º39’S, 60º42’W), determining the minimum sample, index of relative importance (IRI), size of prey, feeding efficiency, dietary selectivity, amplitude of the trophic niche, standardization, circadian rhythm of feeding activity and habitat preference. The trophic spectrum was made up of 17 taxonomic entities, mainly fishes (IRI = 16,000), followed by mammals and amphibians (IRI = 8,000). The highest percentage of prey size was found in the interval 151 -> 200 mm. The amplitude of the trophic niche ranged between 1.98 and 4.21, and the feeding efficiency between 89.9% and 99.9%. In relation to dietary selectivity, the correlation between abundance of prey in stomachs and abundance of prey in the study area yielded no significant results (rs = 0.078, P > 0.001). The rhythm of feeding activity responded to the bell-shaped model. Aquatic vegetation was the unit of vegetation and environment selected more frequently.