Studies on the fluctuation of numbers of Long-tailed Tits along slopes of the River Tenryu, Nagano

Abstract

1. This study on the Long-tailed Tit was made during February 1956 and August 1959, at the slopes along the River Tenryu, Kamigo-mura, Shimoina-gun, agano.2. Seasonal fluctuation in the number of individuals and flocking behaviour are described.3. Seasonally, the number of individuals was maximum in mid. and late June and minimum in late March.4. Sudden big change of number was characteristic, showing the movement by flock unit.5. In two years of the study, 30% of the yearly maximum remained to breed within the study area. The breeding success was ca. 70%, and rates of increase after breeding was about 140% and 180%.6. The types of fluctuation of the number of individuals were: 1) January-March With lowest number but least variable. 2) April-May Number suddenly increased by occurrence of family flocks. 3) June-July With maximum nember of individuals. 4) August-December Number less than maximum but with frequent fluctuation between 10-30 birds.7. Seasonal flock classification was possible as follows: 1) February-April Period of pair formation. 2) May Period of 'family flocks'. 3) June-July Period of a 'large joint flock'. 4) August-October Period of breaking up into 'medium, and small joint flocks'. 5) November-January Period of 'winter flocks' and formation of home range.8. The flocks of the study area had communication with those of adjoining areas, especially in the period of 'large joint flock' of the summer.9. One to two winter flocks of the total of 20 individuals inhabited a belt of area about 120 km2. But, occasional imigration of the flocks of other areas and the emigration of some early wandering flocks were noticed.