A winter hill bird census at southwest skirts of Tokyo

An example of census analysis

Abstract

In January, 1968, nine bird censuses by random line transects were made through five different habitats on the hills of Mizonokuchi along the west side of Tamagawa River, s. w. of Tokyo. The five habitats were : low rice paddy areas narrowly stretched along the valley, dry cultivated fields on the hill, land for sale in plots on hill bordered by brushy thickets with a few trees, small old villages with some vegetation remaining at the lower slopes of the hill and mixed woods developed at the ends of valleys.
The census area covered some 2.5 km along NW-SE of the hill. The census was made 50-105 minutes during morning or afternoon and the time required to pass through each habitat was recorded so that relative bird densities could be expressed by No./per hour.
Analyses of relative abundance, habitat preference, "commonness", areal bird density, etc. were made by calculating the following ratios and indices (No. means the number of bird indivduals):
A. Occurrence rate in time…Frequency recorded/Total censuses (9 times) %
B. Occurrence rate in place…Number of habitats the species was recorded/Total number of habitat (5 habitats) %
C. "Commonness index"…³√A×B×Toal No. tallied of the species
D. Average number…Mean of numbers recorded in all habitats where the species occurred
E. Species dominance…No. tallied of a species /No. tallied of all species (%)
F. Relative species dominance…% of mean No. of a species relative to the mean No. ef the most numerous species which is regarded as 100
G. Index of abundance…√A(Occurrence rate in time)×D(Average number)
H. Density…No./per hour
I. Areal dominance…No. tallied for a habitat/No. tallied for habitats (%)
J. Relative areal dominance…% of total No. for a habitat relative to the habitat of the largest total No. which is regarded as 100
K. Areal density…No. per hour of all species in each habitat
L. Habitat preference rate… % of No. per hour of a species in a habitat/Total of No.per hour of this species in all habitats
M. Carrying rate of the habitat…No. of species recorded/No. of indivduals counted (%)
N. Carrying index of the habitat…√Tot. No. of species×Tot. No. of individuals
Based on these calculations, shown by Tables 1-9, bird faunae and carrying rates of five habitats were compared and the habitat preference of birds and habitat value as feeding or resting place, or cover, were considered for chief species, also in relation to their flocking or moving rates.
In all, 22 species were recorded of which the Tree Sparrow Passer montanus was most numerous in number using all five habitats and gathered on rice paddies with the preference rate of 48%, as a joint feeding place and were found scattered, with the rate 24%, in villages in small numbers, next prefering hill areas and least using wooded valleys. Its flocking rates in these habitats could be compared calculating: flock number, flock size, its range and mean x±δ, flocking rate (√range×x) and relative flocking rate (regarding the highest flocking rate as 100). Next common species was the Grey Starling Sturnus cineraceus with 100% occurrence rate in time but not using the plots of land for sale. Its chief preference as feeding place was wet rice paddics with the preference rate of 60% as compared with 10% for dry cultivated fields on the hill, and occurred 26% in the village using it as resting (and feeding when tree-berries were available) place. The bulbul Hypsipetes amaurotis widely moved except on the rice paddies and used village trees and valley woods with the preference rate of 30-32%, then plots of land for sale 27%, and sometimes used, with the rate 10%, cultivated hill to feed on buds of vegetables.