The identity of one of the more problematic vagrants brought to Christmas
Island by the tropical low which became Cyclone Rosie in April has been
resolved. Ian McAllan found the bird on 21 April and it was still there when
Tony Palliser, Frank O'Connor and I left the island on 28 April. Having
listened to the recording, Paul Holt is absolutely certain that this bird
which we reported as an Acrocephalus Warbler was in fact a Locustella
Warbler - a Pallas's Grasshopper Warbler L. certhiola. No wonder it was so
skulking and no wonder we couldn't find a match among the several
Acrocephalus songs investigated!
Ian McAllan obtained a tape recording of the bird. Tony Palliser had
digital copies made and distributed them to various experts in Chinese,
Indonesian and SE Asian birds. That species has a prominent broad off-white
supercilium as reported by Ian McAllan, bordered above and below by black as
reported by Tony Palliser, (hence 'Black-browed Reed Warbler'). So why did
we think by it's song that it was a Reed Warbler? Kevin Baker in Warblers of
Europe, Asia and North Africa says this under 'Voice'.
"Song begins with a series of soft even feeble, ACROCEPHALINE-like
disjointed phrases, followed by a louder, musical, high-pitched and rapid
swee-swee-swee or sewee-seewee-seewee which is repeated five to seven times.
These phrases can be highly variable, some ending with a musical
chow-chow-chow, chack-chack etc. Another variation might be rendered tic tic
tactac-zzz-chackchack-zzz-chow-chow-chow. Call notes include rapid, thin
ticking tik-tik-tik and short trilling chi-chirr or chir-chirr; also a sharp
chirk or chuck."
An excellent description of what we heard. Pallas's Grasshopper Warbler
is a winter visitor to the Greater Sundas and therefore likely to occur on
Christmas Island.
Now to confirm the various Swiftlets, the Elegant Tern and (for others),
Silver-backed Needletail. The Tiger Shrike, Asian House Martin and House
Swifts are straight forward.
Mike Carter
30 Canadian Bay Road
Mount Eliza VIC 3930
Tel (03) 9787 7136
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