sábado, 30 de maio de 2015

The contribution of the Tyto alba feeding ecology to confirm bat species occurrence in north Portugal

Bat skull remains identified in Barn owl pellets collected from north of Portugal: a - Upper canine of the Western barbastelle (Barbastella barbastellus) with elongate section and flat inner surface with a sharply defined cingulum; b - lower mandible of the Grey long-eared bat (Plecotus austriacus) with a salience on the processus angularis in the posterior part; c - a depressed and the dorsal profile of the European free-tailed bat (Tadarida teniotis) is straight and almost horizontal. The arrows indicate the respective distinctive morphological details

The Barn owl (Tyto alba) is an opportunistic species which feeds mainly on small mammals but also on birds, bats, reptiles, amphibians, insects and fishes. With regard to bats, several studies in Europe suggest that this group constitutes a small portion of the Barn owl diet representing less than 1% of its prey items. Through the analysis of 2,934 Barn owl pellets, collected between 2006 and 2014 in 27 sites/nests located in north Portugal, the remains of six bats belonging to five species were identified in a total of 9,103 prey items identified: the Western barbastelle (Barbastella barbastellus), the Grey long-eared bat (Plecotus austriacus), the Brown long-eared bat (Plecotus auritus), the European free-tailed bat (Tadarida teniotis) and the Common pipistrelle (Pipistrellus pipistrellus). These findings are of great interest as they represent new data on the Brown longeared bat and European free-tailed bat distributions, and allow to confirm an historical record of the Western barbastelle in the region.
However, although the number of items found in Barn owl pellets is residual, the data collected for bats may represent very important contributions, particularly for rare species, such as Western barbastelle, or species classified with the conservationist status of “data deficiency”, as in the case of Western barbastelle, Brown long-eared bat and European free-tailed bat. This is of particular relevance, since even in the most recent Atlas of bats in Portugal the data on the distribution of some species remain very scarce and incomplete, especially for species like the Western barbastelle, which is confirmed only in about 10% of the total of 1,008 10X10km grid cells. Additionally, for bat species that are difficult or impossible to distinguish by acoustic methods, such as Brown long-eared bat, less than 2% of the referred grids were confirmed.

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