Friday, August 18, 2017

Distribution and age-specific plumage states of the long-tailed cuckoo (Eudynamys taitensis)

TitleDistribution and age-specific plumage states of the long-tailed cuckoo (Eudynamys taitensis)
Publication TypeJournal Article
Year of Publication2013
AuthorsGill, BJ, Hauber, ME
JournalNotornis
Volume60
Issue2
Pagination158-170
Type of ArticleFull article
Keywordsage-classes, distribution, Long-tailed Cuckoo, New Zealand, plumage, sex ratio
Abstract

Plumage states of the long-tailed cuckoo (Eudynamys taitensis) are reviewed and summarised from examination of museum study-skins. Besides the distinctive adult plumage (barred above, white background colour below) and immature plumage (spotted above, pale brown below), some birds (13% of those in the wintering grounds, plus 1 bird from New Zealand) show a “transitional” plumage presumed to be intermediate between the immature and adult condition. Also, some pale birds found in New Zealand may represent a hitherto-unrecognised juvenile plumage. A review of distribution records (museum specimens plus published sight-records) in both the summer and winter ranges of the cuckoo confirms a vast fan-shaped distribution extending 6,000 km north from New Zealand to the tropical Pacific, and 11,000 km from east to west in the tropics. Wake Island (19.3°N) in the north, Palau (134.5°E) in the west, Henderson Island (128.3°W) in the east and the Snares Islands (48.0°S) in the south are the extreme records in this range. Records of museum specimens reveal that almost all long-tailed cuckoos returning to New Zealand in October are in adult plumage. Autumn records show a gradual northward retreat of cuckoos within New Zealand, with a stronger-than-average bias in North Island records from March to May. There is no equivalent North Island bias for the spring influx in September and October. Museum specimens from eastern Polynesia exhibited an uneven sex ratio biased towards males (74%), whereas the sex ratio elsewhere was more even. Our study confirms the vast total range of the long-tailed cuckoo and provides age-specific details of the seasonal waxing and waning of the migratory patterns of the breeding population within New Zealand.

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