Comparative Feeding Ecology of the Alpine Accentor Prunella collaris on Mt. Hakusan and Mt. Norikura

Abstract

A comparative study of feeding ecology of the Alpine Accentor (Prunella collaris) populations breeding on Mt. Hakusan and Mt. Norikura was conducted in June and July, 1994. To capture and band the birds, artificial feeding grounds using millet seed were established on the top of both mountains. In June, Alpine Accentors on Mt. Hakusan did not respond to the supplemental food and fed on insects on snow surfaces, while those on Mt. Norikura used the feeding grounds frequently and foraged mainly in snow-free areas (rocky slopes and alpine deserts). The main foraging habitat of Alpine Accentors on both mountains shifted to alpine meadows in July. In June, the average number of insects per 50×50cm quadrat taken on snow surfaces on Mt. Hakusan (117.5) was much greater than that on Mt. Norikura (24.0). In July, the average number of insects per quadrat was 8.4 and 4.7 on Mt. Hakusan and Mt. Norikura, respectively. Hemiptera constituted the main taxa, accounting for 79.7% of 395 samples collected. Aphids were the most frequent of the Hemiptera identified to family level, accounting for 87.3% of 315 Hemiptera. These insects were brought by updrafts from lowlands to the alpine zone. We conclude that Alpine Accentors on Mt. Hakusan relied less on supplemental food because they foraged on abundant insects which were easy to capture and detect on snow surfaces. The breeding unit of Alpine Accentors is a group consisting of about seven members who share a large territory. It is possible that the different food items in each mountain population have different effects on group size, range size and timing of reproduction.