Author ' s personal copy Short communication Diet and breeding success of long-eared owls in a semi-arid environment

Only a few studies, and mostly in temperate climates in Europe, have examined the breeding and diet of long-eared owls (Asio otus) compared to studies of cavity-breeding owls, possibly because of the difficulties in reaching the nests of the former. Here we studied a population of long-eared owls, monitoring the diet of breeding owls and that of owls at a communal roost, every two to three months during 2006 e2009, in a semi-arid region in Israel. It was found that the studied owls produced more young than in most countries in Europe. Diet was not associated with breeding parameters of the owls, whereas laying date was negatively correlated with both clutch size and number of nestlings. We found that more social voles (Microtus socialis) and fewer birds and house mice (Mus musculus) made up the diet at nests than that of adults at the roosts. The diet and breeding of long-eared owls in Israel differ from that in Europe, with birds and mice comprising an important part of the diet, in addition to voles. 2012 Elsevier Ltd. All rights reserved. Even though long-eared owls (Asio otus) are common over much of the Holarctic, most studies have concentrated strictly on the diet of these owls, due to the ease of pellet collection and analysis (Marti, 1976; see review; Birrer, 2009), while fewer studies have dealt with breeding (Korpimäki, 1992; Sergio et al., 2008; Tome, 1997; Village, 1981), most likely due to the difficulty in reaching their nests, compared to cavity-breeding owls that use nest boxes. In Europe, long-eared owls show strong numerical and functional responses in breeding numbers and diet to changes in vole density (Korpimäki, 1992; Korpimäki and Norrdahl, 1991; Sergio et al., 2008; Tome, 2003a; Village, 1981). Those studies that have dealt with variation in the diet of long-eared owls were carried out in Europe (Korpimäki, 1992; Korpimäki and Norrdahl, 1991; Nilsson, 1981), with a consequent need to study this owl’s diet in other climates in order to determine whether a similar pattern of diet specialization and breeding occurs in other populations breeding in different climates and thousands of miles away from Europe. This is important because in regions where owls are highly specialized predators on one prey species, they may become more generalist in prey selection or nomadic when their preferred food is less available. Unlike in Europe, where cold harsh weather may limit the breeding of owls (Altwegg et al., 2006; Lehikoinen et al., 2011), in semi-arid environments it is high temperatures that may affect diet and breeding (Charter et al., 2010b). Here we studied a population of long-eared owls that breed in a semi-arid region of the Middle East, in Israel, at a study site where temperatures can rise above 40 C during the breeding season. In Israel, long-eared owl populations have increased during the last decade, probably because of a rise in the number of nest sites and greater availability of food in the region, as a result of the increased crow population (hooded crows, Corvus corone) and themodernization of agriculture, moving from mainly grazing to crop fields and plantations, which in Israel have larger rodent populations than in non-cultivated areas (Motro unpubl. data). However, owl diet has been little studied (Kiat et al., 2008; Leader et al., 2008) and breeding success even less so (Charter et al., 2010a) in the Middle East. Here we present a study on the diet of long-eared owls in a semi-arid area, specifically relating to whether the diet of adults and nestlings differs and whether diet is associated with breeding in long-eared owls. The study was performed in the Jezreel Valley, Israel (32 310N, 35 150E), 80e90 m above sea level, with a semi-arid climate. The site comprisedmostly arable fields (sweet corn, alfalfa, oats andwheat), orchards (grape, almond plantations, olive groves, citrus), and scattered small villages. Although long-eared owls bred in both nest baskets attached to eucalyptus trees (Eucalyptus sp.) (Charter et al., 2010a) and in natural crows nests, only the former were monitored during the 2007e2009 breeding seasons (18.1 %e31.6% of nest baskets were occupied). Active nests (defined as a nest in which eggs were * Corresponding author. Present address: Department of Evolution and Environmental Biology, University of Haifa, 31905, Haifa, Israel. Tel.: þ 972 544901130; fax: þ972 36406010. E-mail address: charterm@post.tau.ac.il (M. Charter).