G'day All
Tom has reminded us of a useful practise: that of having a good look
at individual swifts in a flock. It is the best way of finding other
species including swiftlets, but be really careful not to mistake
martins for swiftlets.
You do have to be careful and have a good long look, as White-
throated Needletails themselves vary a lot in size. Australian skins
in Australian museums of WTNT have a wing measurement range of
184-217 mm (live birds I have caught varied: 192-220 mm). Weights in
museum specimens varied 54 - 154 gm. This has a strong bias on the
light side as many museum skins came from birds that had crashed and
died after days of not eating - during which time they would have
been using up their fat reserves. My sample of live bird weights is
108-126 g.
In trying to differentiate the other needletails you need to look for
whether or not there is a white patch on the back between the wings
or not, Whether the lores are white & whether the throat is white or
brown. The Papuan Needletail has a white throat, chest & stomach &
is a much more dumpy bird, looking much shorter than the needletails.
Key to Needletails
Species White lores White back White throat
White-throated NT yes yes yes
(Juv) yes brown yes
Silver-backed NT yes yes
brown
Brown-backed NT no brown Dk brown
Purple NT no no
Black
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Michael Tarburton
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www.birding-aus.org
birding-aus.blogspot.com
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