On October 16, I posted a Hawk Identification Exercise to the list. I
finally got a summary done of the inputs I received. Thanks to the 25
people who participated. On October 17, I updated the web page to
include size information for the bird.
If you want to take another look at the web page for the exercise it is
http://ahart.homeip.net/hawkid2.html
The final vote tally was:
Sharp-shinned - 23
Cooper's - 2
There were three people who initially voted Cooper's, but changed their
vote to Sharpie when I posted the size information.
Why people said Sharp-shinned
-----------------------------
Head comparatively small (11)
Narrow white terminal band on tail (8)
Uniform color of head and nape (7)
Outer tail feathers same length as inner (square tail) (6)
Rounded head (5)
Overall size of bird (5)
Head (cap) and back are same color - crown not dark (4)
Less substantial tarsus/talons (4)
No neck (4)
Relatively short tail (3)
Pale eyebrows (thin pale suprecilium) (2)
Light mottling on the back - only a few spots
Yellow orbital ring
Small bill
Tawny colored auriculars
Why people said Cooper's
-----------------------------
rounded tail (4)
thick tarsus (3)
pale nape (3)
eye more forward on the head
bill
spots on the back
white supercilium
thick tarsus
large head
broad terminal band on tail
coopers often perch on fence posts or poles, sharpies almost always
perch on tree branches
Some thoughts on the results
-----------------------------
One of the distinguishing features mentioned in many of the references
is the shape of the folded tail. In a Cooper's it is rounded, and in a
Sharpie it is square. I think some people are confused by that
description. I think a more appropriate way to describe the difference
is that in a Cooper's the outer tail feathers are shorter than the inner
ones. While in a Sharpie, the outer tail feathers are roughly the same
length as the inner ones. In the picture where the bird's back faces
the camera, you can see that the outer feathers are approximately the
same length as the inner feathers - so as six of the participants
pointed out, the folded tail shape appears "square" points to Sharpie.
An interesting thing about some of the votes for Cooper's is that they
specified specific field marks but made the opposite call on those marks
from what other people did. The most common was the "rounded tail" that
I just discussed. The second most common was the feet of the bird.
Several people felt that this bird had substantial feet that seemed to
be consistent with a Cooper's - In fact one of the people who picked
Sharpie made the comment that at first he thought the bird was a
Cooper's because of the feet, but when he looked at all the indicators
he was convinced it was a Sharp-shinned.
Project Feederwatch has a nice set of web pages with identification
hints for Cooper's versus Sharp-shinned. The URL is
http://www.birds.cornell.edu/pfw/AboutBirdsandFeeding/accipiterIDtable.htm
One interesting comment on the Feederwatch pages was mentioned by one of
the people who thought this bird was a Cooper's. According to the
Feederwatch site, Sharpie's almost never perch on fences - that is
Cooper's behavior. The Sharp-shinned in my pictures apparently doesn't
have Internet access - so she didn't know she was not supposed to be
perched on my fence :-)
Thanks to all of you who participated - I hope you all enjoyed the exercise.
Hopefully a nice Cooper's will come sit on my fence sometime soon and
pose for me like this bird did. Then we can have some nice side by side
comparison pictures.
References mentioned by the participants
National Geographic Field Guide to the Birds of North America
Hawks - Peterson series
Wheeler & Clark - Photographic Guide to N. Am. Raptors
Wheeler & Clark - Hawks of North America, 2d ed.
Kenn Kaufman's - Advanced Birding
Thayer's Birding Software
Sibley's Guide to the Birds
Brian K. Wheeler's "Raptors of Eastern North America"
Johnsgard's Hawks, Eagles, and Falcons of NA
Peterson's Guide - fifth edition
Project feederwatch web pages
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