Comparative termporal prey use by barn owl (Tyto alba) and little owl (Athene noctua) in the Evros Delta, Northeastern Greece HARALAMBOS ALIVIZATOS1, VASSILIS GOUTNER2*, ANDREAS ATHANASIADIS3 and KOSTAS POIRAZIDIS4 1 4 Zaliki Street, Athens 11524, Greece 2 Department of Zoology, School of Biology, Aristotle University, 54124 Thessaloniki, Greece 3 Evros Delta Information Centre, Traianoupoli 68100, Greece 4 WWF Greece, Dadia project, Dadia, Soufli 68400, Greece Abstract The diets of barn owl (Tyto alba) and little owl (Athene noctua) were studied in the Evros Delta from 2002 to 2004 through pellet analysis. The barn owl preyed primarily on mammals (mainly Microtus, Mus and Crocidura), while birds and amphibians were much less important. Mean prey biomass ranged from 11.5 to 16.1 g. The median prey biomasses and mammalian prey use differed significantly during the study (p < 0.001). The diet of the little owl was primarily composed by insects (mainly Coleoptera, Orthoptera and Dermaptera) and mammals (mainly Microtus and Mus), although birds were also of some importance. Mean prey biomass ranged from 2.2 to 12.2 g. Overall, the median prey biomasses differed seasonally (p<0.001). Between owls, the median prey biomasses mostly differed seasonally. Prey diversity and evenness were both higher in the little owl. The seasonal distribution of the main prey taxa differed significantly in the little owl being similar in the barn owl. In cluster analyses, diet was clumped mainly by owl species and study years, and secondarily by seasons. The same analysis for mammalian prey suggested common prey use based on their availability and differences were probably due to different behaviour of prey species and predators.   < back .