Re: Those amazing TWINNED EMU FEATHERS! - Question

[Ronald Orenstein <ornstn@home.com>]

At 12:06 AM 12/06/2000 -0400, Ray Stanford wrote:
>    Amazed, I asked them two questions:  (1) Do all Emus have twinned 
> feathers?; and, (2) Are all feathers on all Emus twinned?
>
>     The answer was yes, to both questions.

Your friends are correct.  The "twinned" part is technically referred to as 
an aftershaft or afterfeather.  According to "A Dictionary of Birds":

"This is a structure resembling a feather in miniature attached to the 
underside of the feather at the superior umbilicus. Six types may be 
recognized of which the most developed is that found in Casuariiformes 
[including emus - RO], where the afterfeather closely resembles the main 
feather, so that each feather appears double.  In its simplest type the 
afterfeather lacks an afterrshaft (hyporachis) and merely consists of a row 
of barbs (an aftertuft) attaching to the rim of the superior umbilicus.  It 
is found in the New World Vultures (Cathartinae).  Several groups entirely 
lack afterfeathers, eg Ostrich, pigeons, cuckoos and swallows.  Most 
workers assume that the function of afterfeathers is to increase the 
thermal insulating property of the feathers.... some birds, eg ptarmigans, 
have larger afterfeathers in the winter than in the summer plumage."


--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@home.com