IN THE SCOPE
Sharpie vs. Coop, Part I: In Flight
Tony Leukering
Despite the plethora or even the over-abundance of field guides
covering ABA-area raptor identification, many birders struggle to
differentiate Sharp-shinned and Cooper’s hawks. Familiarity grows
from repetition and one of the challenges many of us face is getting
that repetition with these two small accipiters. As an example, a reasonably active Colorado birder could expect to see 1,000 (perhaps
more) Yellow-rumped Warblers in a year, and I would suggest that
racking up good looks at 1,000 or more of almost any species would
give most birders a pretty good handle on the field identification of
that species. (Of course, I assume that one will actually study each
of those 1,000 Yellow-rumpeds, not quickly pass most of them off
as “just another butter-butt.”) Yet, I would bet that that same birder
would see no more than 20 Sharp-shinned Hawks in a year, and many
of those sightings would likely be poor, fleeting and/or of perched
birds, leaving perhaps just a few good looks at flying Sharpies in that
year.
Another source of small-accipiter misidentification has to do with
the variability of size and posture these birds exhibit in the field. We
read that Sharpies have square-ended tails, while Coops have roundtipped tails. We’ve learned that the leading edge of the wings on
a flying Coop are straight, with the head projecting well forward,
while the head on a flying Sharpie barely protrudes beyond the jutting wrists of the bird. And of course these things are often true. But
sometimes the converse is also true, that is, these features can send
you down the road to small-accipiter perdition. While these shape
features can be quite useful in field identification, it’s important to
know that exceptions exist.
A Solution, or Some Parts Thereof
One thing that Pete Dunne, Clay Sutton, David Sibley, Brian
Wheeler and Jerry Liguori have in common is they’ve each spent
hundreds of hours at hawk watches observing Sharpies and Coops
in flight. Where else is one going to rack up 1,000 good looks at flying individuals of each species in a time frame that enables actual
use of the knowledge gained? So if you can, visit a hawk watch and
spend some time studying flying hawks. If you own one or more of the
hawk-ID guides (e.g. Dunne et al. 1989, 2012, Liguori 2005, 2012,
Wheeler 2007) study the pictures and illustrations, but also read the
text. But getting back to tail-tip shape and head/wing posture, check
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out the photos on the back-cover and see if you can pin a name to
either of the birds depicted in them.
Tail-tip shape: While it is true that, generally, Sharpies have
square-tipped tails and Coops round-tipped tails, it is not true for
every individual of either species. There are Sharpies that exhibit
fairly rounded tail tips and there are many, many Coops that sport
square tail tips. Variation in tail-tip shape in accipiters is due to many
factors, the most important of which are age and sex, though wear
and molt status also play a part at particular times of year. In general,
adult accipiters sport squarer-tipped tails than do juvenile accipiters.
In my experience, there is great individual variation, but male accipiters tend to have squarer-tipped tails than do female accipiters.
Somewhat exacerbating this difference in tip shape is that adults and
males have shorter tails (relative to overall length) than do juveniles and females. So, considering both Sharpie and Coop together,
the shortest and most-squared tails (often even notched) are found
on adult male Sharpies, while the longest and roundest-tipped tails
belong to juvenile female Coops. Please note that these are tendencies, not absolutes.
Perhaps the most important aspect of tail-tip shape in small-accipiter ID is the relative lengths of the outermost rectrix (rectrix 6 or r6)
and the innermost rectrix (r1) on either side of the tail. With Sharpies, the individual tail feathers are all of approximately the same
length, thus with the tail closed the outermost is as long as any other
rectrix. Coops, however, have graduated tails, with the r6 on each
side being obviously shorter than the middle pair. On most individual
Coops, the r5 is also shorter than r1, but longer than r6. The difference in lengths of r1 and r6 on some adult male Coops can be fairly
minimal, making for a very nearly square tail tip. It is also important
to remember that a fanned tail, regardless of how squared it appears
when folded, is rounded. Think of an old-fashioned hand fan or holding playing cards spread out in your hand – all the spines of the hand
fan are the same length and the playing cards are all the same length,
but they take on a round-tipped appearance when spread.
Head/wing posture: Again, generally, Sharpies tend to fly with
their wrists jutted forward, thus partly or mostly eclipsing their small
head. It’s also true that Coops often fly with the leading edge nearly
razor-straight from wingtip to wingtip, with their big head jutting
well forward. However, it is not true at all times, in all flight behaviors. When Sharpies look around while in flight, they seem to
elevate and extend their heads, giving them a very different appearance. Additionally, wing posture in flying birds is dependent upon
myriad variables, some of which change on a second-to-second basis
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requiring alterations in wing shape by the bird. A bird flying into a
headwind uses a different wing shape than does one flying with a
tailwind. A gliding raptor will pull its wing tips in and jut its wrists
out. A soaring accipiter of any species will have a straight or even
concave (wing tips farther forward than wing base) leading edge to
the wings.
Back-cover Photos
As you might imagine, I selected photos of two juvenile accipiters
with malice and forethought. So, which set of dogma, if any, takes
precedence in these pictures? Both birds have squared tails, however,
the upper bird (Fig. 1) has the wrists jutted nearly as far forward as the
tip of the head, whereas the lower bird (Fig. 2) has a nearly straight
leading edge to the wing, with its head projecting far forward.
The bird in Fig. 1 is a Cooper’s Hawk. It was photographed in a
glide, thus its wrists are jutting forward giving it a somewhat smallheaded appearance. Looking at the tail feathers on this Coop, note
that the r6s on both sides of the tail stick out a bit off the tail’s sides,
thus showing that the tip of each of those outermost rectrices falls
obviously short of the tips of the r1s. You should also be able to see
on the tail’s left side that the left r5 also sticks out, handily showing
the location of its tip, and showing the feather to be longer than the
corresponding r6, but shorter than the corresponding r1. Because the
Coop is holding its tail closed fairly tightly, the tip of what is actually
a fairly rounded tail appears square.
The bird in Fig. 2 is a Sharp-shinned Hawk. It appears “big-headed” and “straight-winged” because it was photographed lifting and
extending its small head in order to look around. Its wrists, though
not jutting far forward, are still the farthest-forward points on the
wings. Additionally, this bird shows the typical juvenile Sharpie underparts pattern of streaking on the chest and barring on the sides,
both of which are fairly ill-defined. Beware that this pattern can be
approached by a small minority of juvenile Coops, but such individuals still retain the white (rather than creamy/off-white) ground color
to the underparts typical of Sharpie. The final point on this bird is
the long outermost tail feather on both sides of the tail.
Fig. 1 (back cover). Juvenile Cooper’s Hawk, Kinch Road, Huron County, MI, 18
May 2014. Photo by Tony Leukering
Fig. 2 (back cover). Juvenile Sharp-shinned Hawk, Kinch Road, Huron County,
MI, 1 May 2014. Photo by Tony Leukering
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ACKNOWLEDGMENTS
I appreciate review of a previous draft of this essay by Jerry Liguori.
LITERATURE CITED
Dunne, P., D. Sibley, and C. Sutton. 1989. Hawks in Flight. Houghton Mifflin Harcourt,
New York.
Dunne, P., C. Sutton, and D. Sibley. 2012. Hawks in Flight, 2nd ed. Houghton Mifflin
Harcourt, New York.
Liguori, J. 2005. Hawks From Every Angle. Princeton Univ. Press, Princeton, NJ.
Liguori. J. 2011. Hawks At a Distance. Princeton Univ. Press, Princeton, NJ.
Wheeler, B. K. 2007. Raptors of Western North America. Princeton Univ. Press, Princeton, NJ.
Tony Leukering, [email protected]
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Fig. 1
Fig. 2
In the Scope
Sharpie vs. Coop, Part I: In Flight . . . 319