| ANALYSIS OF DIETS OF UPLAND BUZZARDS USING STABLE CARBON AND NITROGEN ISOTOPES |
LAI-XING LI A1, XIAN-FENG YI A1, MING-CAI LI A1, XIAO-AI ZHANG A1
A1 Northwest Institute of Plateau Biology, Chinese Academy of Sciences (CAS), 59 Xiguan Street, Xining 810001, Qinghai, P.R. China
We measured the stable carbon and nitrogen isotope ratios for muscles of the upland buzzards (Buteo hemilasius) and their potential food sources, plateau pikas (Ochotona curzoniae), Qinghai voles (Lasiopodomys fuscus), plateau zokors (Myospalax fontanierii), and several passerine bird species at the alpine meadow in Maduo county, Guoluo prefecture of Qinghai province, People's Republic of China, to provide diet information of upland buzzards, highlighting different diet composition of upland buzzards exposed to different locations. The results demonstrated that stable carbon isotope ratios of upland buzzards, passerine birds, plateau pikas, plateau zokors, and Qinghai voles were -24.42 0.25‰, -22.89 1.48‰, -25.30 1.47‰, -25.78 0.22‰, and -25.41 0.01‰, respectively, and stable nitrogen isotope ratios were 7.89 0.38‰, 8.37 2.05‰, 5.83 1.10‰, 5.23 0.34‰, and 8.86 0.06‰, respectively. Fractionation of stable carbon and nitrogen isotope ratios between upland buzzards and their food were 1.03‰ and 2.11‰, respectively. Based on mass balance principle of stable isotopes and the Euclidean distance mixing model, upland buzzards depended mainly on plateau pikas as food (74.56%). Plateau zokors, Qinghai voles, and passerine birds only contributed a small proportion (25.44%) to diets of upland buzzards. The results were closely accordant with analyses of stomach contents and food pellets, which firmly supported the feasibility of using stable carbon and nitrogen isotope ratios to investigate diet information of upland buzzards. Another study based on stable carbon isotopes showed that upland buzzards living in the Haibei prefecture (another prefecture located in the southeast Qinghai province) mainly preyed on passerine birds (64.96% or more) as food supply. We were alarmed by the preliminary results that widespread poisoning activities of small mammals could reshape the food composition of upland buzzards, influencing the stability and sustainability of the alpine meadow. Bio-control on rodent pests should be carried out rather than the chemical measures.
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