Hello Con,
That is a little funny. Sorry you are asking the questions in the wrong
sequence. Yes your observation of the flying Welcome Swallow is correct! In all
birds the central tail feathers are always above the outer tail feathers. The
central tail feathers are always on top. That is regardless of whether it is
the outer or the inner tail feathers which are longer or if they are all the
same length. Sure sometimes they can get ruffled but that is temporary. In
birds like chickens that fold their tail in an upside down V, it can be
confusing.
The wing is the same, the central feathers are above the outer feathers. This
is always the case. If it was the other way then the tail and wing would help
the bird lose altitude when flying.
Hence the difference between the swallow (forked tail) and the flycatchers
(graduated tail). That difference is simply quantitative.
Philip
-----Original Message-----
From: Con Boekel
Sent: Wednesday, 5 October, 2016 5:30 PM
To: canberrabirds chatline
Subject: On the way in which tails with graduated or stepped tail feathers are
stacked
A later edition of the Slater's has an illustration intended to assist
in separating the Broad-billed from other flycatchers. The illustration
compares the way in which the ends of the tail feathers are stepped
close together in one species compared with the ends of tail feathers
which are stepped gradually - such that the ends of successive sets of
feathers recede towards the undertail coverts instead of the rump. This
in relation to when the bird is perched and in which the tail is not
spread during flight.
The result is that the longer tail feathers are on top and the shorter
tail feathers are underneath the longer feathers.
I was asked whether the illustration was intended to show the underneath
of the tail or the top of the tail.
I responded immediately that I only knew of occasions where the tail
feathers were stepped on the underneath so that the longer tail feathers
were always above the shorter tail feathers.
But, just now studying an image of a flying Welcome Swallow, taken from
above, I was somewhat surprised to observe that the shorter tail
feathers appear to be situated over the longer tail feathers.
Correspondence will be entered into.
regards
Con
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