Diet and Food-niche overlap of the Little Owl (Athene noctua) and Common Kestrel (Falco tinnunculus) in Shir-Ahmad Wildlife Refuge, Sabzevar

Study on pellets is one of the best non-invasive methods to determine nutrient contents which have been eaten by a predator bird. The purpose of this study was to examine the diet and food niche overlap in the Little Owl (Athene noctua) and Common Kestrel (Falco tinnunculus) in Shir-Ahmad Wildlife Refuge, Sabzevar. After completing field surveys, pellets were transferred to laboratory. Then, these pellets were separated by soaking. Then prey remains in pellets were separated and indentified. The percentage of each food item was calculated in relation to total number of pellets. In addition, the weight, length, and diameter of pellets, the percentage of prey biomass, the food niche breadth, species diversity, species evenness, and food niche overlap were calculated. Based on total 548 pellets collected of the Little Owl, the diet was consisted of beetles (13.78%), locusts (15.02%), birds (5.02%), small mammals (18.13%), rodents (18.55%), shrews (6.42%), reptiles (0.7%) and ants (2.79%), respectively. Analysis of 206 pellets of the Common Kestrel showed that the diet was consisted of beetles (24.92%), locusts (25.55%), birds (6.54%), small mammals (15.89%), rodents (13.71%), shrews (3.12%), reptiles (4.98%) and ants (5.30%), respectively. In this study, the food niche overlap of the Little Owl and Common Kestrel based on the percentage of overlap's measure, Pianka's measure, and Horn's index was 88.51%, 0.98, and 0.96, respectively. Results of this study showed that food niche overlap between the Little Owl and Common Kestrel was high.