Frequency of Occurrence and Ingested Biomass of Different Prey of the Barn Owl Tyto alba in an Island Ecosystem

Miriam Viganò,Leonardo Ancillotto,Paolo Agnelli,Gentile Francesco Ficetola,Emiliano Mori

doi:10.3390/birds1010002

Abstract

The Barn Owl Tyto alba is commonly reported as a non-selective predator of small mammals, and its diet has been thoroughly analyzed also to assess the small mammal assembly composition in many study areas. The aim of this work was to analyze the diet of the Barn Owl in the Elba island through the analysis of 161 pellets collected in September 2020. Undigested fragments were isolated and compared with reference collections. We confirmed that the Barn Owl is a typical predator of field mice (62% of relative frequency), with synanthropic murid rodents as the second category of prey. The frequency of consumption of shrews increased by 9% with respect to the previous work, suggesting that the natural environment of Elba island is still in a good health status. Moreover, fragments of two newborn hares were detected, increasing the knowledge on the local trophic spectrum of the Barn Owl. Finally, the skull of a Geoffroy’s Myotis Myotis emarginatus confirmed the presence of this species in Elba island after over 60 years from the first unconfirmed record. Repeated studies conducted in the same study site may provide useful information on prey population trends and local environmental status.

Highlights

Widespread wild species, i.e., those showing intercontinental distribution ranges, are suggested to be well-adapted to a number of different environmental conditions, which require a remarkable specific physiological plasticity [1,2,3]
It has been suggested that the Barn Owl diet includes proportionately more birds on islands than in the mainland, as islands are relatively poorer of small mammals [28]
This explains its high frequency in the local diet of the Barn Owl, which is reported as a non-selective predator whose feeding habits depend on the local availability of different prey species [13,46]

Summary

Introduction

Widespread wild species, i.e., those showing intercontinental distribution ranges, are suggested to be well-adapted to a number of different environmental conditions, which require a remarkable specific physiological plasticity [1,2,3]. The Barn Owl Tyto alba is a medium-sized widespread nocturnal raptor distributed in Europe, Africa, Southern Asia, Oceania, North and South America, both on mainland and on islands [12]. The diet of this species has been thoroughly studied [13], in Europe [14,15,16] and America [17,18], given that the analyzing content of egested pellets is easy and cheap [19]. It has been suggested that the Barn Owl diet includes proportionately more birds on islands than in the mainland, as islands are relatively poorer of small mammals [28]. In a review on the diet of the Barn Owl on Mediterranean islands, it has been confirmed that, murid rodents were the commonest prey species, birds and reptiles were 5–18 more represented in the diet of insular

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