27/12/2018
An
unusual warbler discovered on a small Indonesian island as recently as 2004 has
just been described as a new species of leaf warbler. Named Rote Leaf Warbler
after the island in the Lesser Sundas where it was found, Phylloscopus
rotiensis differs from all other species in the genus by its relatively
long, tailorbird-like bill and distinctive coloration.
Although
many islands in the region harbour breeding populations of leaf warblers, Rote
Island – which lies south-west of Timor – was historically not known to have
any. However, while birding on the Tapuafu peninsula in December 2004, Dr Colin
Trainor from Australia's Charles Darwin University observed several warblers
which were "frequent in woodlands and tropical dry forest" and
uttered a "breezy, rising and falling whistle" not unlike that of
Timor Leaf Warbler on the adjacent larger island of Timor.
Five
years later Philippe Verbelen and Veerle Dossche visited Rote Island to observe
and study the birds, and succeeded in making detailed observations and
obtaining a series of photographs. Philippe noticed that the leaf warblers
looked substantially distinct from any other Asian, African or European species
with which he was familiar: "Alarm bells went off when we realised how
strikingly different the bill shape and the coloration of the Rote bird were
compared to all other leaf warblers." The long bill had a yellow-orange
lower mandible, and additionally the undescribed warbler showed a broader and
more yellow supercilium than in Timor Leaf Warbler, a more prominent yellow
crown stripe, warmer yellow sides of the head and underparts, and an
olive-green rather than olive-grey crown.
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