Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!genbank!ames!oliveb!oliven!mjm
From: mjm@oliven.olivetti.com (Michael Mammoser)
Newsgroups: rec.birds
Subject: Re: OUTDOOR: Re: Chicken Hawks
Message-ID: <52342@oliveb.olivetti.com>
Date: 14 Dec 89 04:11:31 GMT
References: <14739@shamash.cdc.com>
Sender: news@oliveb.olivetti.com
Distribution: na
Lines: 88



In article <14739@shamash.cdc.com>, gls@hare.udev.cdc.com (gl sprandel x4707) writes:
> 
>  Re: Chicken hawk
>    Note: Size is not a very good diagnostic for determining
>    coopers versus sharp shinned.
>    I've seem hand held birds a few times and there is a even size gradient
>    from male sharpie, to female sharpie, to male coopers to female.
>    (and then on up to goshawk)
>    Thus after looking at male sharpies for a while, if you see a larger 
>     bird you might think coopers but its more likely a female sharpie.
>     Shape of tail does not work that well during migration during the fall
>     since they may set it differently in heavy migration.
>     What do you all use as a field mark for coopers/vs sharp shinned ?

	As was mentioned in a previous posting, identifying Cooper's
from Sharp-Shinned Hawk is probably the most difficult raptor ID
problem. One should undoubtedly use a number of field marks rather
than rely on just a single one. It may not be possible to identify
every bird that you see.

	There is no documented overlap in size between Cooper's and
Sharp-Shinned Hawk, although female sharpies may "approach" the size
of male coops. Size may be a useful field mark for birds at the
extreme of the range. People living in the southwest should be
aware that the mexican race of Sharp-Shinned Hawk is larger than the
north american race and the western race of Cooper's is smaller than
the eastern. Birds in this area may overlap in wing chord size, but
do not in weight or overall length.

	I agree that tail shape may be misleading when the bird is
fanning its tail, but when folded, I believe that tail shape is an
excellent field mark. Cooper's have tail feathers that are successively
shorter from the inside feathers to the outside, and the shape of
the feather tips is rounded, which gives the Cooper's a more rounded
overall look to the tail. Sharp-Shinned have tail feathers of nearly
equal length, and the shape of the outer feathers is more square,
giving the tail an overall square look. Also, Cooper's Hawks have
an extensive white terminal band on the tail that generally abuts the 
first dark tail band, while Sharp-Shinned have a thin (or absent) white
terminal band that generally abuts the grayish/brown base color of the 
tail some distance from the first dark tail band. Of course, wear in the
tail feathers can obscure this mark to varying degrees. I once observed
an immature Cooper's Hawk whose tail was so worn that it had no white
terminal band at all.

	Cooper's Hawks have proportionally larger heads and longer
necks. They also tend to hold their wings more perpendicular to the
body while soaring. This gives the impression in Cooper's, when
they are flying, that the head sticks out further beyond the leading
edge of the wing.

	Perched Cooper's Hawks have a tendency to raise the feathers
on the back of the neck and head, giving the back of the head a
squared-off look. Supposedly, this behavior has never been reported
in Sharp-Shinned Hawks.

	The eyes of both species are very nearly equal in size and,
with the larger head of the Cooper's and its tendency to raise its 
hackles, its eyes look smaller with respect to the head size. The
eyes also appear to be placed more forward in the side of the head.

	The crown of the adult Cooper's Hawk is somewhat darker
than the back, separated by a pale nape, which produces a sharp
line of contrast at the junction of the nape and crown. The adult 
Sharp-Shinned Hawk has a crown nearly equal in color to the back, 
without a pale nape and no apparent contrast.

	The streaking on the undersides of immature Cooper's Hawks
is finer and darker than immature Sharp-Shinned. Also, the streaking
on Cooper's diminishes on the belly, while that on Sharp-Shinned
remains dense.

	An excellent article on identifying accipiters was published
in Birding magazine a few years ago and details the above mentioned
field marks. I don't know what month or year it was, but it was in
volume XVI, number 6.

	I believe that it is easier to see field marks on perched
birds rather than those that are flying. Soaring birds tend to be
too far away to make out most diagnostic field marks and birds that
aren't soaring are generally in view for only a short time. I sure
don't envy hawk counters who usually have to make an ID on soaring
accipiters during migration. However, the more birds that you look
at, the better you will get. There is no substitution for experience.

Mike