An analysis of the movements of the Spangled Drongo in eastern Australia (late 1800s-mid 1990s)

摘要

Movements of the Spangled Drongo Dicrurus bracteatus in eastern Australia were examined using records (n = 3461) from the first Atlas of Australian Birds of the Royal Australasian Ornithologists Union from 1977 to 1981, and records from Sydney and Wollongong, New South Wales, from 1981 to 1990 (n = 160), data from unpublished studies, banding information and a comprehensive review of the literature before 1995. Three distinct movements were recognised, all of which were linked to the breeding season in spring and summer. First, there was a southward migration in Queensland during spring, immediately before the breeding season, and a northward return movement in autumn. The southward migration comprised subspecies D.b. atrabectus andD.b. bracteatus north and south of the Burdekin Gap, QId, respectively. This movement was obvious from Torres Strait to Rockhampton and was concentrated near the coast, whereas the northward return movement in autumn was spatially more widespread. Second, there appeared to be an eastward movement immediately after the breeding season from the eastern slopes of the central Great Dividing Range to lower coastal areas within a few kilometres of the sea, and a corresponding westward movement in spring. This altitudinal movement comprised only the subspecies D.b. bracfeafus.lt was evident between latitudes 21°S (Mackay, QId) and 31°S (Nambucca Heads, NSW), and was sometimes small in scale with respect to distance from, or elevation above, the sea. Third, there was a small southward movement of birds of subspecies D.b. bracteatus in NSW in autumn, immediately after the breeding season, and a northward return movement in spring. This southward movement was evident from Forster (32°S) to the far south coast of NSW, whereas the corresponding northward return was less obvious. Spangled Drongos that moved southwards in NSW in autumn were confined mostly to coastal areas <15 km from the sea. It is proposed that the Drongos moving southwards in NSW in autumn are an extension of the D.b. bracteatus population that descends altitudinally eastwards and overwinters on the coast in southern Queensland and northern NSW.