Analysis of mixed flocks of tits in the Botanical Garden of Tohoku University, Sendai

Abstract

1. In October 1962-January 1963 and October 1963-January 1964, foraging behavior of tits and other species forming mixed flocks were observed at Botanical Barden of Tohoku University in Sendai, for the purpose of analysis of interspecific relations.2. During winter season, the foraging differed by species in the following manners: the Longtailed Tit Aegithalos caudatus took food mainly from bark and foliage; the Great Tit Parus major from bark, foliage and ground; the Coal Tit P. ater from foliage, bark and cones; and the Goldcrest Regulus regulus from leaves of conifers (by hovering), foliage and bark.3. Statistically, the percentage frequencies of foraging patterns differed by species significantly, with confidence intervals in 60% reliability (Kato 1955), showing that each species in mixed flocks takes food by its own specific foraging method.4. The same statistical comparison, by confidence intervals in 60% reliability, was applied to the analysis of foraging patterns of each species in mono-specific (Sf) and mixed flocks, with (Mf+) or without (Mf-) Long-tailed Tit.As the result, the Long-tailed and Great Tits showed no change in their specific foraging patterns in either kind of mixed flocks (Sf, Mf+ or Mf-). But, significant change occurred in the foraging patterns of Coal and Willow Tits, as well as Goldcrest, when they belonged to diffrent kind of mixed flock. These three species should therefore be affected by the presence of other species, especially through the interspecific attacks.5. Judging from the number of interspecific supplanting attacks and of approach-avoidance, the Great Tit is most aggressive among these flock forming species, the Coal Tit being the second, and Long-tailed Tit, Willow Tit, and Goldcrest are in lower ranks as for aggressiveness, but the order of aggressiveness among these three species are not clear.6. It is suggested that the order of aggressiveness of each species forming mixed flocks is different from the leading order of foraging movements of mixed flocks.