BREEDING BIOLOGY AND DIET OF THE LONG-LEGGED BUZZARD (BUTEO RUFINUS) IN THE EASTERN JUNGGAR BASIN OF NORTHWESTERN CHINA YI-QUN WU School of Life Science, Lanzhou University, Lanzhou, Gansu 730000 China MING MA Xinjiang Institute of Ecology and Geography, Chinese Academy of Science, Urumqi 830011 China FENG XU Institute of Zoology, Chinese Academy of Science, Beijing 100080 China DIMITAR RAGYOV Central Laboratory of General Ecology, Bulgarian Academy of Sciences, Sofia 1113 Bulgaria JEVGENI SHERGALIN International Wildlife Consultants (U.K.) Ltd., P.O. Box 19, Carmarthen, SA33 5YL U.K. NAI-FA LIU 1 School of Life Science, Lanzhou University, Lanzhou, Gansu 730000 China ANDREW DIXON 2 International Wildlife Consultants (U.K.) Ltd., P.O. Box 19, Carmarthen, SA33 5YL U.K. ABSTRACT.—The eastern Junggar Basin in northwest China is a potential area of sympatry for breeding Long-legged Buzzards (Buteo rufinus) and Upland Buzzards (B. hemilasius). However, during a breeding season survey in 2005, the Long-legged Buzzard was the only species recorded present in this semidesert region. The minimum breeding density within our survey area was 0.19 breeding pairs/100 km 2 and all nests were located either on rock faces or clay cliffs. There was little overlap in the location of Long-legged Buzzard and Golden Eagle nest sites, possibly as a result of interspecific competition. We present here information on clutch size (mean 5 3.3 eggs), brood development, and fledging success (0.7 chicks per breeding pair), as well as on the diet during the breeding season. Mammalian prey, especially the great gerbil (Rhombomys opimus), made up most of the diet of Long-legged Buzzards. KEY WORDS: Long-legged Buzzard; Buteo rufinus; China; diet; reproductive rate. BIOLOGI ´ A REPRODUCTIVA Y DIETA DE BUTEO RUFINUS EN EL ESTE DE LA CUENCA DE JUNGGAR DEL NOROESTE DE CHINA RESUMEN.—El este de la cuenca de Junggar en el noroeste de China es un a ´rea de potencial simpatrı ´a entre Buteo rufinus y B. hemilasius. Sin embargo, durante un muestreo realizado en la e ´poca reproductiva del an ˜o 2005, B. rufinus fue la u ´nica especie registrada en esta regio ´n semidese ´rtica. La densidad mı ´nima de individuos reproductivos en nuestra a ´rea de muestreo fue de 0.19 parejas reproductivas/100 km 2 y todos los nidos se encontraron en paredes de rocas o en acantilados de barro. Hubo poca sobreposicio ´n en las ubicaciones de los nidos de B. rufinus y de Aquila chrysaetos, probablemente como resultado de competencia 1 Email address: naifaliu@sohu.com 2 Email address: falco@falcons.co.uk J. Raptor Res. 42(4):273–280 E 2008 The Raptor Research Foundation, Inc. 273