Barn owls as biological control agents: potential risks to non-target rare and endangered species M. Zaitzove - Raz 1,2 , O. Comay 1,2,3,4 , Y. Motro 5 & T. Dayan 1,2 1 School of Zoology, Tel Aviv University, Tel Aviv, Israel 2 The Steinhardt Museum of Natural History, Tel Aviv University, Tel Aviv, Israel 3 Department of Ecosystem Services, German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany 4 Department of Ecosystem Services, Helmholtz Centre for Environmental Research, Leipzig, Germany 5 The Plant Protection and Inspection Services, Ministry of Agriculture and Rural Development, Beit Dagan, Israel Keywords barn owls; biological control; rare rodents; endemic species; psammophiles; Israel. Correspondence Michal Zaitzove - Raz, School of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel. Email: zaitzoveraz@mail.tau.ac.il Editor: Karl Evans Associate Editor: Michael Schaub Received 29 April 2019; accepted 12 February 2020 doi:10.1111/acv.12576 Abstract Rodent agricultural pests cause significant food loss every year. Attempts at mitiga- tion via chemical pest control may cause secondary poisoning and harm non-target species. Biological pest control by bolstering barn owl Tyto alba populations through the provision of artificial nest boxes is in use in several countries. The national biological pest control project of Israel began in the early 1980s in the Mediterranean zone and was subsequently expanded to the northwestern Negev desert, including areas adjacent to nature reserves and natural sand dunes, a threat- ened habitat in Israel. We analyzed prey of barn owls in the northwestern Negev to determine whether owls preyed on non-target endemic, threatened rodents. A total of 14 632 prey items were collected from 95 nesting boxes between 2013 and 2016. We found that barn owls feed on protected and locally endangered species such as Gerbillus andersoni allenbyi (vulnerable  VU), Gerbillus pyra- midum (VU), the endemic Meriones sacramenti (endangered) and Gerbillus gerbil- lus (critically endangered). These species constitute a significant proportion of barn owl diets (sometimes more than half of the prey items in a single nest box), espe- cially in areas under 5 km from sand dunes, suggesting that bolstering the barn owl population may threaten locally endangered species. It could be hypothesized that agricultural crops serve as a resource for endangered species, allowing their numbers to increase, in which case their conservation status should be reassessed. However, extensive rodent trappings in agricultural fields in the region revealed <1% Gerbillus individuals, while in nearby dunes only gerbils were trapped. Insuf- ficient data are available to assess whether or not M. sacramenti could have become a local pest. Our study highlights the risks that may be associated with the use of barn owls as rodent control agents in areas where natural open landscapes and nature reserves are interspersed with agricultural landscapes. Introduction Rodents are significant agricultural pests (e.g., Stenseth et al., 2003); rodent agricultural damage includes a high abundance of nesting burrows in fields, gnawing on produce and banding of tree barks. Furthermore, rodents also harm and destroy agricultural equipment, such as water pipes (Poch e et al., 1982; Tobin & Fall, 2004). Studies have found that the extent of damage from rodents varies with the type of agricultural crop, habitat and region. Anticipated annual chronic crop damage of 5–15% can increase in years of rodent irruption up to 80% of yields. Therefore, control of rodents in agricultural landscapes is an important economic goal (Singleton et al., 1999; Stenseth et al., 2003; Hodara & Poggio, 2016). Farmers commonly use pesticides to control rodent popu- lations. The major drawback to this practice is that it may result in secondary poisoning of non-target organisms such as red fox Vulpes vulpes and raptors feeding on the poisoned rodents (Burns & Connolly, 1995; Hosea, Finlayson & Lit- trell, 2001; Eason, Ross & Miller, 2013; Geduhn et al., 2015; Hindmarch & Elliott, 2018). There is currently a glo- bal effort to develop and implement holistic approaches to sustainable and environmentally friendly agriculture that involve, among others, the reduction in the use of toxic chemicals in agriculture (Hosking, Sullivan & Welsby, 1994; Kremen & Merelender, 2018). Smith (1919) defined classical biological control as controlling the population of pests with the help of their natural specific enemies. The development of biodiversity friendly agricultural practices includes the Animal Conservation  (2020) – ª 2020 The Zoological Society of London 1 Animal Conservation. Print ISSN 1367-9430