Distribuiçao, abundância e estrutura populacional de peixes introduzidos no rio Guaraguaçu, Paranaguá, Paraná, Brasil

Abstract

The diets of the Burrowing Owl (Athene cunicularia Molina, 1782) and the Barn Owl (Tyto alba Scopoli, 1769) were analyzed in seven areas in the City of Curitiba and in the Municipality of Colombo, State of Paraná, Brazil. A total of 77 owl pellets were analyzed, from which 1891 prey items were identified, with an estimated biomass of 2701.94 g. The identified prey were distributed among 5 classes, 10 order, 11 families, 5 subfamilies and 8 genera. Dietary analyses were based on the number of consumed prey items, the estimated biomass of each prey item, the frequency of each prey item in the owl pellets, and the relative importance of each prey item in the diet according to the Relative Importance Index of Pinkas (1971). The niche breadth of Levins (1968) was also computed for the trophic niche of the two owl species. The diet of A. cunicularia includes mainly a large number and variety of insects, as well as rodents and anurans to a lesser extent. In all five areas where A. cunicularia was studied, the most abundant and important prey items were orthopterans. Rodents were mostly murids. There was seasonal variation in the diet of A. cunicularia, with a larger abundance of arthropods in the rainy seasons. The diet of T. alba was basically composed of rodents, particularly cricetids, with a lower frequency of anurans and arthropods. This species seems to display a diet that is more adapted to the subtropical climate of the region. The differences in the diets among areas are discussed in terms of the characteristics of each area.

The diets of the Burrowing Owl (Athene cunicularia Molina, 1782) and the Barn Owl (Tyto alba Scopoli, 1769) were analyzed in seven areas in the City of Curitiba and in the Municipality of Colombo, State of Paraná, Brazil. A total of 77 owl pellets were analyzed, from which 1891 prey items were identified, with an estimated biomass of 2701.94 g. The identified prey were distributed among 5 classes, 10 order, 11 families, 5 subfamilies and 8 genera. Dietary analyses were based on the number of consumed prey items, the estimated biomass of each prey item, the frequency of each prey item in the owl pellets, and the relative importance of each prey item in the diet according to the Relative Importance Index of Pinkas (1971). The niche breadth of Levins (1968) was also computed for the trophic niche of the two owl species. The diet of A. cunicularia includes mainly a large number and variety of insects, as well as rodents and anurans to a lesser extent. In all five areas where A. cunicularia was studied, the most abundant and important prey items were orthopterans. Rodents were mostly murids. There was seasonal variation in the diet of A. cunicularia, with a larger abundance of arthropods in the rainy seasons. The diet of T. alba was basically composed of rodents, particularly cricetids, with a lower frequency of anurans and arthropods. This species seems to display a diet that is more adapted to the subtropical climate of the region. The differences in the diets among areas are discussed in terms of the characteristics of each area.