[birdky] Answer to Quiz Bird #3 (long)

[Mark Monroe <markmonroe1@xxxxxxxxx>]

I'm sure everyone is ready to hear the solution to
Quiz bird #3, so here it is. :)  The original picture,
and a follow-up picture (I think it will be posted
shortly at least), can be found at
http://www.biology.eku.edu/KOS/whatisit.html

Ok, first the 'easy' part of the quiz.  From quick
examination of the bird, it is noted that it has a
hooked beak and what appear to be strong feet with
sharp talons.  This should quickly lead one to believe
it is a raptor of some sort.  Now, since this view of
this bird is lacking any size reference or overall
shape hints, plumage is the quickest means of
narrowing down the birds identity.  It is clear from
the picture that the bird has an orange barred belly
that does not extend below the legs, a banded tail
with many wide dark and pale bands, barred flight
feathers, and dark grey upperparts (as evidenced by
the cap and upperside of the wing).  Only two species
of raptors in our area have all of these field marks,
adult Cooper's Hawk and adult Sharp-shinned Hawk.

Now comes the tricky part.  There are many field marks
to distinguish these two birds in the field.  However,
we are rarely treated with a view that supplies them
all.  Such is the case with this bird.  In Cooper's
Hawks, the tail is proportionately longer than in
Sharp-shinned and the outer tail feather is
significantly shorter than the innermost tail feather
(this is what causes the curved tail appearance). 
However, the tail is clearly not visible in this
picture.  

The next best field mark on adult Accipiters is the
nape color.  In Cooper's Hawks, the nape is paler than
the grey on top of the head, which creates a 'capped'
look to Cooper's while the nape color is uniform with
the head and back in Sharp-shinned.  However, again,
this picture does not provide those details. 

Now, seeing as our best field marks are absent, we can
try to deduce this bird's identity through its
structure.  First we can look at the head.  The head
of a Cooper's Hawk is proportionately much larger than
a Sharp-shinned (in flight this leads Cooper's to look
like a flying cross while Sharp-shinneds look like a
"T".  However, the bird in this picture is obviously
dead and the head is at a strange angle, so it is
difficult to discern if the head really is that big. 
However, one clue that can be used is that although
Cooper's have much larger heads than Sharp-shinneds,
the eye is approximately the same size in both
species.  This leads the eye of the Sharp-shinned to
take up a large percentage of the head, while the eye
appears small on the head of a Cooper's.  In this
picture, the eye definitely does not dominate the
head, so we have our first hint that perhaps this is a
Cooper's.  The beak also appears 'impressive',
suggestive of a Cooper's.  In my experience,
Sharp-shinned beaks tend to be weaker looking, much
like a Budgerigar's (parakeet).  However, these
features simply are suggestive of Cooper's, not
definitive.  

We can then move to the legs.  The Sharp-shinned Hawk
has much thinner legs than a Cooper's (which leads to
the 'sharp-shinned' appearance) and much smaller feet.
 In this picture, the right tarsus is visible and
appears somewhat thick (suggestive of Cooper's), but
the left foot, from what is visible, is not very
impressive (suggestive of Sharp-shinned).  Having
struck out here, we can try some deductive reasoning.

In Accipiters, the males of the species are smaller
than the females, and Sharp-shinneds are smaller on
the whole.  However, male Cooper's and female
Sharp-shinneds are close enough in size that without
some sort of reference, they can be very difficult to
distinguish.  This bird certainly is striking of a
'tweener' (slang for in-betweener) based on the lack
of definitive appearance in the head, legs, and feet. 
So, that would suggest to us that we are most likely
dealing with a male Cooper's or a female
Sharp-shinned.  Now, in Accipiter's, the males of both
species are more strongly marked with darker plumage
than the females (this is more evident in Cooper's,
but both species show a difference).  When I first saw
this photo I commented to Brainard that the bird
appeared very dark based on the upperside of its wing.
 Too dark IMO for a female of either species.  Given
the above evidence, I submit that I 'felt' this bird
was a male Cooper's Hawk.

Ok, having said all of that, I still would not
identify this bird with 100% confidence based on the
one photo and would submit it as Unidentified
Accipiter on something like a Christmas Count or hawk
watch.  I feel that far too many times a specific name
is placed on a bird when there isn't sufficient
evidence to identify it.  In fact, I sent this initial
photo to a few colleagues (hawk watchers and banders)
with mixed, and all non-committal, results.

In this particular case, we have the luxury of asking
for a second photo from the individual who found the
bird, something that would not happen if you caught a
glimpse of this bird in your backyard.  The photo is
of the underside of the tail and clearly shows the
outer tail feathers are shorter and that the bird is
indeed a Cooper's Hawk.  Knowing that much, I feel
equally as confident that the bird is a male based on
structure and plumage.

Keep those quiz photos coming and happy birding!

Mark

Mark Monroe
University of Michigan

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• Follow-Ups:
  • [birdky] Re: Answer to Quiz Bird #3 (long)
    • From: Scott Marsh

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[birdky] Answer to Quiz Bird #3 (long)

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