皇居内の鳥類調査概況(1968年度)

抄録

This is the 4th year report of bird census in the Imperial Palace during April 1968 and March 1969. Out of 74 species recorded since 1965, 48 species (52 species in 1967) were found with additions of only one species and one hybrid (Mallard × Sptbilled Duck). The Palace area includes ponds with summer heronries and winter duck flocks (mostly Spotbilled Duck and Mandarine Duck) and average number of species and birds recorded per one census was 23.6 species (23.8 in 1967). and 481.0 birds (641.2 in 1967). The census was made monthly (14 times in all) and usually 10.00-12.00a.m. along the same 4km route. Previous reports are in Nos. 25, 27, 29 of this journal.