Abstract
The diets of the Barn Owl Tyto alba and the Short-eared Owl Asio flammeus have been extensively studied worldwide over the past few years, especially on the Iberian Peninsula. Nevertheless, very few studies have examined the diets and the trophic niche overlap in areas where these two raptor species occur in sympatry. As such, in this study we compared the diets of the Barn Owl and the Short-eared Owl inhabiting agricultural landscapes of the Vega de Granada, south-east Spain, based on pellet analysis. The diets were very similar, as both owls preyed mainly on small mammals, the Algerian Mouse Mus spretus being the prey most commonly found in pellets from both species. Although the diet of the Barn Owl was more diverse than that of the Short-eared Owl, the food niche overlap was very high, thus indicating a low interspecific trophic segregation. Despite the similarities between both diets, the frequency of the Mediterranean Pine Vole Microtus duodecimcostatus was much higher in pellets from the Barn Owl, thus suggesting that the Barn Owl may exert pest control in years when the Mediterranean Pine Vole occurs in high numbers.
Highlights
The diet of a species varies mainly according to food availability, which is one of the main drivers of trophic niche differentiation (Schoener 1974), as well as with the interaction with other ecologically related species (e.g. Adams & Rohlf 2000)
Similar species that show allopatric distributions usually exploit the same resources (Lopes et al 2020), whereas some degree of trophic niche segregation takes place when they live in sympatry (Gambale et al 2020)
The selection of different prey groups by sympatric species explains food niche segregation processes in areas where raptor species exhibit a food niche overlap of 47–73% (e.g. Thorstrom 2000, Navarro et al 2003, Zhao et al 2011, Romanowski & Lesiński 2019)
Summary
The diet of a species varies mainly according to food availability, which is one of the main drivers of trophic niche differentiation (Schoener 1974), as well as with the interaction with other ecologically related species (e.g. Adams & Rohlf 2000). Raptors with similar diets coexist more frequently when prey diversity is higher, as this allows niche segregation (Moreno-Rueda et al 2009). Interspecific trophic segregation can be induced both by the abundance and body size of prey, as well as the foraging strategies and activity time of the raptors ( Jaksić & Braker 1983, Leveau et al 2004, García & Arroyo 2005), a transition to opportunism in sympatric raptor species may occur because of a lack of direct competition for food (Gerstell & Bednarz 1999). The selection of different prey groups by sympatric species explains food niche segregation processes in areas where raptor species exhibit a food niche overlap of 47–73% (e.g. Thorstrom 2000, Navarro et al 2003, Zhao et al 2011, Romanowski & Lesiński 2019)
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