Diet And Trophic Niche Of Four Sympatric Raptors

Diet and trophic niche of four sympatric raptors was analyzed by pellets and remnants analysis technique. Pellets of were collected from the Altun Mountain National Nature Reserve in Ruoqiang County. Food composition and proportion of four raptors were identified by comparative analysis. Then the diet niche and overlap was analyzed. Three small mammals and several species of bird and insect were consumed. We found that small mammals were the most important food items by checking the frequency of each food composition in pellet samples. Small mammals accounted for 95.18% of food composition and contributed 99.35% of biomass in pellets. There were significant differences in the prey composition between summer and winter(χ2=52.27,df=4,P<0.01). There were significant seasonal differences in small mammal’s average tibial length(P<0.01). For the full year, average mammalian tibia length consumed by little owl is 19.45 mm ± 5.84mm(n = 194), mainly for(10.01mmⅡ-20.00mm) and(20.01mmⅢ-30.00mm) rating of prey(46.39 % and 48.45%, respectively). Trophic niche breadth of little owl in Altun Mountain Nature Reserve is up to 2.583 in summer, and lowest is 0.949 in winter. It indicated that the difference of food items and predation rate of prey species was related to the availability of prey resources in the habitat and the little owl was an opportunism predator.The results showed that a total of 4 mammal species and several bird species were eaten by upland buzzard. By checking the frequency of each food category in pellet samples, we found that small mammals were the main food items. Plateau pika(Ochotona curaoniae) was the most common species of the mammalian prey, which constituted 82.27% of the total prey. Small mammals were the most important food item, and accounted for 92.61% of food composition. Biomass contributions of small mammals in pellets were 95.13%. The results showed that a total of four species were eaten by long-legged buzzard, including three mammal and one bird species. By checking the frequency of each food composition in pellet samples, we found that small mammals were the main food items. Plateau pika(Ochotona curaoniae) was the most common species of the mammalian prey, which constituted 86.96% of the total prey. Small mammals were the most important food item, and accounted for 95.09% of food composition. The biomass contributions of plateau pika in pellets of were 97.39%. The results showed that a total of four species were eaten by Falco cherrug, including three mammal and one bird species. By checking the frequency of each food composition in pellet samples, we found that small mammals were the main food items. Plateau pika(Ochotona curaoniae) was the most common species of the mammalian prey, which constituted 87.13% of the total prey. Small mammals were the most important food item, and accounted for 92.02% of food composition. The biomass contributions of plateau pika in pellets of were 97.59%. Regardless of the number of individuals or biomass, plateau pika is the most important food type of raptors.Shannon- wiener diversity index, Pielou’s evenness and food niche breadth index of little owl is the highest, the lowest is long-legged buzzard. The trophic niche overlap is large(0.871-0.98) from the point of view of species composition but is small based on size of the composition of food(tibia length 0.644-0.884, mandibular length 0.086-0.771) among four Raptor species. Four raptors feed different size of foods. The high degree of food overlap among four sympatric raptors from the Altun Mountain National Nature Reserve indicated significant competition for food resources. The diet analysis results show that the raptors will play an active role in rodent pest control. The results of our study have important guiding significance for management of small mammals in Alpine desert and grassland.