Thursday, December 13, 2018

From wetlands to islands: morphological variation, plumage and song in Pacific island Acrocephalus warblers

TitleFrom wetlands to islands: morphological variation, plumage and song in Pacific island Acrocephalus warblers
Publication TypeJournal Article
Year of Publication2018
AuthorsBell, BD
JournalNotornis
Volume65
Issue4
Pagination202-222
Type of ArticleFull article
KeywordsAcrocephalus, body-size, evolution, islands, Pacific, reed-warbler, song
Abstract

Acrocephalus warblers occur across Eurasia, Africa, and Australasia, where they are typically migratory, wetland species, but also occur on islands as sedentary endemics in drier habitats, including forest and scrub. External morphology and song amongst Pacific island Acrocephalus warblers were investigated and comparisons made with Acrocephalus species elsewhere. There was a range of sizes between Pacific island Acrocephalus warblers, many being larger than migratory continental species. Bill:wing length ratios were higher in most Pacific species, and their wings more rounded, than most continental species, but less rounded than swamp-warblers of Africa and adjacent islands. Plumages of W and N Pacific species resembled reed-warblers elsewhere, but in SE Polynesia were more varied, brown or grey dorsally, shaded olive, yellow or rufous, and pale ventrally, shaded white, yellow or buff-white, with a melanistic morph on Tahiti. Spectrographic analysis showed a gradient of song complexity from continental and Marianas/Micronesia species (A. hiwae, A. syrinx), through to A. taiti and A. vaughani on the Pitcairn islands, which had no song. The mean frequency of Pacific island reed-warbler songs was inversely correlated with mean body size.

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