| Food is a link between animal and environment, not only for the animals needed for survival and reproduction of material and energy, but also the establishment of animal communities in a variety of species relations. A systematic studies of diet habitat and interspecific relationship among red fox Vulpes vulpes, common kestrel Falco tinnunculus and long-legged buzzard Buteo rufinus were completed by fecal analysis from 2002 to 2008 in the southern Junggar basin, Xinjiang Uygur Autonomous Region, China. The diets of three carnivores were determined using two fecal-analysis method: numerical percentage and biomass contribution; and the interspecific relationship among the three carnivores were measurement of niche overlaps, Pianka index and competitive coefficient.1. We analyzed 385 fecal samples to discuss the feeding habit of red fox. Results revealed that small mammals (69.85%) are the primary diet for red fox, and insects (16.12%), reptiles (11.36%), plants (7.69%) and birds (4.76%) as follows. The most important biomass contributions of prey group in fecal of red fox was Lepus capensis (60.08%), and then was Meriones spp. (19.56%). Diet compositions of red fox changed greatly from pup rearing period to dispersal period, the percentage of dietary composition between the two periods was significantly different (Pearsonχ2=43.729, df=15, P<0.001). The food diversity of red fox in the whole period was 1.937, and in pup rearing period was 1.865, then was 1.848 in dispersal period, and the evenness index was 0.699, from 0.727 in pup rearing period to 0.700 in dispersal period, thus the standardized Levins'index was 0.223, from 0.267 to 0.246.2. We studied the diets of common kestrel by fecal analysis, 798 food pellets were collected in the study area. Results showed that small mammals (66.21%) are the primary diet for common kestrel, and insects (17.77%), birds (8.36%) and reptiles (7.66%) as follows. The main food throughout the two period was Meriones spp., based on the biomass contributions was 52.40% of prey group in common kestrel's food pellet, and then was Rhambomys opimus whose biomass contributions was 32.13%. There was significant variation in diet in breeding period and non-breeding period, the percentage of dietary composition between the two periods was significantly different (Pearsonχ2=75.469, df=15, P<0.001). In the breeding period, the food diversity of common kestrel (H'=1.822) was lower than non-breeding period (H'=1.901), while evenness and standardized Levins'index (E=0.711, Bsta=0.256) were higher than non-breeding period (E=0.702, Bsta=0.253). The food diversity, evenness and standardized Levins'index in the whole period were 1.928, 0.695 and 0.230, respectively.3. We collected and analyzed 367 food pellets from long-legged buzzard in the study area. Results revealed that small mammals are the primary diet for long-legged buzzard, then insects, reptiles, plants and birds were accounting for 73.78%, 13.61%, 7.93% and 4.70% of diet, respectively. The main percentage of biomass contributions of those preys to long-legged buzzard diet was Rhambomys opimus, which contributed 50.99%, then was Meriones spp., with the biomass contributions was 29.00%. There was great significance in diet composition of long-legged buzzard between breeding period and non-breeding period, based on the Pearson Chi-square test of the percentage of dietary composition between the two periods (Pearsonχ2=69.633, df=15,P<0.001). In the breeding period, the food diversity of common kestrel (H'=1.610) was lower than non-breeding period (H'=1.626), while evenness and standardized Levins'index (E=0.669, Bsta=0.258) were higher than non-breeding period (E=0.616, Bsta=0.206). The food diversity, evenness and standardized Levins'index in the whole period were 1.718, 0.620 and 0.206, respectively.The niche overlaps, Pianka index and competitive coefficient of red fox and common kestrel, common kestrel and long-legged buzzard, long-legged buzzard and red fox were 0.678-0.778-0.653, 0.568-0.626-0.981, and 0.765-0.885-1.397, respectively. The result shows that there was a intense competition and coexistence among them. The competition coefficient between red fox and common kestrel was relatively low, and between common kestrel and long-legged buzzard, and between long-legged buzzard and red fox were higher. According to the competitive exclusion principle, a complete competitor can not coexist. Although the three predators had a high degree of niche overlap between them, but they coexistence in the arid zone of Junggar basin, and we thought that the choices of the diet were divided, and the contingency-table test also showed, the percentage of dietary composition between them were significantly different, based on optimal foraging theory, we speculated that the red fox preferred to prey Lepus capensis, the common kestrel tended to prey Meriones spp., and the long-legged buzzard was biased in favor of Rhambomys opimus.
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