皇居内の鳥類調査概況(1967年度)

抄録

1. This is the third year report on the result of monthly bird censuses made during April 1967 and March 1968 in the Imperial Palace along a same 4km route, usually 10.00-12.00 a.m. The census in the Akasaka Palace was not made this year.
2. A wooded area of Fukiage, with ponds and watercourse and the moat area with duck winter resort and summer heron colony, were separately tallied.
3. In Fukiage area, for example, the average number of species recorded per day, with seasonal change in species, was 19.4, 16.6 and 15.8 in years 1965, 1966 and 1967, and the average number of birds recorded per day was 215.5, 179.8 and 163.4 respectively; thus slightly decreasing.
4. The annual tallies of species recorded were 56, 54 and 52 in years 1965, 1966 and 1967, but new species were added in 1966 and 1967, the totals increasing to 64 and 73 species respectively.
5. The relative abundance of species was compared by occurrence rate, mean number, dominance rate and density index (√mean no.×occurrence rate %) for years 1965, 1966 and 1967.
6. It was confirmed by eight all day counts that the Carrion Crow flocked as winter resort in the Imperial Palace as in the previous year and up to 1500 birds were tallied comming in to the Palace from the morning feeding place (but possibly not roosting). This flock disappeared in April. The Jungle Crow, on the other hand, is permanently resident in the Palace in a flock of scores. These appear to be a nonbreeding young group, and nesting territorial pairs have been found nesting at various places of outer part of the Palace and at 1km apart from it.
7. As a rare straggler, the hoopoe was added to the bird list of the Palace.
8. Feral cats may be influencial as predator especially to the Green Pheasant which showed decrease, and five examples of other birds found by scattered feathers may have been also due to the cats.
9. Nine herons were seen dead, presumably poisoned by insecticides in their feeding grounds.