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Diets of barn owls differ in the same agricultural region.

Article Excerpt
The diet of Barn Owls (Tyto alba) is well known throughout the world because of their cosmopolitan distribution and ease of pellet analysis (Taylor 1994), a method that accurately represents what they consume (Raczynski and Ruprecht 1974). Long-term changes in the diet of Barn Owls are often the result of intensification of agriculture and landscape management (Love et al. 2000). Local variation in diet in different habitats has been described in Europe and the United States (Buckley and Goldsmith 1975, de Bruijn 1994, Taylor 1994, Rodriguez and Salvador 2007), and the diet of Barn Owls in Pakistan differed between districts (Mahmood-ul-Hassan et al. 2007a, b). Barn Owl's are among the most common species of owls in Israel (Shirihai 1996), but studies on their diet have either concentrated on one habitat in one area (Kahila 1992, Pokines and Peterhans 1997, Yom-Tov and Wool 1997, Tores and Yom-Tov 2003, Tores et al. 2005, Charter et al. 2007), or in several areas (Dor 1947), but not in different habitats at a local scale.

Barn Owls occur in most agricultural regions and are mostly specialist predators of small mammals but vary in species hunted according to prey availability (Taylor 1994, Tores et al. 2005). Voles are often the most dominant prey in Barn Owl diets throughout most of the owl's range in the northern hemisphere, probably because of their relative high body mass and ease of capture (Taylor 1994). The Levant vole (Microtus socialis guentheri) is a major pest species of leafy crops in Israel (Moran 2003), and is found at especially high densities in alfalfa fields (Bodenheimer 1949). The house mouse (Mus sp.) and Tristram's jird (Meriones tristrami tristrami) are also common rodents, and are considered agricultural pests (Moran 2003). However, their densities differ between habitats (M. Charter, unpubl. data). In addition, the number of bird species has been shown to increase with vegetation layers and habitat diversity (Moiler 1984) with more species in heterogeneous landscapes than in homogenous arable landscapes (Hanowski et al. 1997, Moreira et al. 2005).

We compared diets of Barn Owls breeding in three different types of habitats (villages, date plantations [Phoenix daetylifera], and alfalfa fields) in the same agricultural region to examine whether diets differed between different habitats within one relatively small agricultural area.

METHODS

The study site (90 [km.sup.2]) was an agricultural region in the Beit She'an Valley, Israel (32[degrees] 30' N, 35[degrees] 30' E), 150 to 250 m below sea level. The climate is arid with maximum and minimum mean daily temperatures (Mar-Jul 1999) of 32.3[degrees]C and 16.7[degrees]C, respectively, and average yearly rainfall of 267 mm (2001-2006).

Oral pellets and prey remains were collected from 20 nests at the end of the...

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