Bird research at Musashi Imperial Tomb area (Occasional report 2)

The Great Tit at the roost

抄録

1. In the winter of 1959-1960 the Great Tits which roosted in the nesting boxes were studied.
2. On December, 38 of 80 boxes supplied in the study area of c. 40ha. had been occupied by the birds. A same bird tended to occupy the same box or several ones in a definite area.
3. The number of the box-roosters declined gradually toward the end of March, probably due to heavy mortality among the Great Tits population in the last winter.
4. Although the number of the box-roosters decreased, the sex ratio among the population was nearly constant; the males always outnumbered the females, the percentage of males being on the average 70 per cent.
5. A simple experiment to test the selection of the roosting sites by the Great Tits revealed that the direction of the entrance holes of the boxes is of little importance.