Zoological Studies

Vol. 45 No. 2, 2006

Comparison of Three Common Methods for Studying the Diet of Nestlings in Two Accipiter Species

Kuang-Ying Huang1, Yao-Sung Lin1, and Lucia Liu Severinghaus2,*

1Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan 106. E-mail: kyhoung@ms8.hinet.net
2Research Center for Biodiversity, Academia Sinica, Taipei, Taiwan 11528

Kuang-Ying Huang, Yao-Sung Lin, and Lucia Liu Severinghaus (2006) Food provisioning to 4 Accipiter virgatus nests and 2 A. trivirgatus nests was monitored during 1998 and 2000 in Yangmingshan National Park, Taipei, Taiwan. We made direct observations of prey deliveries and collected prey remains and pellets throughout the breeding seasons in order to compare the effectiveness and efficiency of the different diet analysis methods for these 2 raptor species. The method of using prey remains worked best for A. virgatus for all measurements, producing 45.23% of all prey items found, 45.23% of all prey items identified to prey taxa, and 38.87% of all prey items identified to species. The observation method worked best for A. trivirgatus, providing 41.05% of all prey items and 18.95% of prey items identified to species, but the proportion of prey items identified to prey taxa was highest using the pellet method (37.37%). Time efficiency was consistently the highest for the prey remains method in A. virgatus. In contrast, for A. trivirgatus, the pellet method was most efficient for assessing the number of prey items delivered and the number identified to prey taxa, but the prey remains method worked best for identifying prey to species. Combining the prey remains and pellet methods increased the prey taxa identified to 81.63% for A. virgatus and 58.95% for A. trivirgatus. Although the value of direct observation has been stressed by many researchers, its effectiveness varied between these 2 species studied in Taiwan.

Key words: Prey delivery, Prey remains, Pellet analysis, Accipiter, Diet analysis.

*Correspondence: E-mail: zobbowl@gate.sinica.edu.tw