The effects of arthropod abundance and size on the nestling diet of two Parus species

Abstract

Feeding habits of Parus major and P. varius inhabiting coniferous plantations of Cryptomeria japonica and Larix kaempferi, each containing a small area of deciduous broad-leaved trees, were analyzed in relation to the abundance and size distribution of arthropods. In a C. japonica-dominated (CJ) area, C. japonica trees were mainly used by P. major only, while deciduous broad-leaved trees were used by both Parus species. In a L. kaempferi-dominated (LK) area, both Parus species used L. kaempferi trees and deciduous broad-leaved trees. The composition of nestling diets differed between Parus species. For prey size, the difference in the breadth was smaller and the overlap was larger between areas than between species. These results suggest that each Parus species preferred a specific size class of prey. That is, the single-prey loader P. major preferred large prey, whereas the multiple-prey loader P. varius preferred small prey. The abundance and size distribution of arthropods greatly differed among foraging microhabitats. Both Parus species selectively used foraging microhabitats according to their prey-size preference.