Here is a recent post from the Union Bay Watch Blog published by Larry Hubbell, long-time local photographer and birder.
Here also is an in-depth article about Larry and his work.
Accipiter Uncertainty
Earlier this month, on the west side of Union Bay, I noticed an accipiter cruising south across the cattails. Even though I was headed in the same direction I quickly lost sight of the small, swift predator. Hoping the hawk might stop to rest, I resolved to check every potential perch I passed. A few minutes later, I saw the shape of a bird in a distant tree. I did a double take. It was crow-sized, but the tail was too long for a crow.
With the bird on my right, I paddled as far to left as the little islands would allow and did my best to not stare. Mentally, I had my fingers crossed, desperately hoping that my passing would not flush the bird. A few years before, I had prepared for moments like this by covering my bright yellow kayak with brown paint. Not wanting to create any flashy reflections, I also covered the white lettering, which proclaims the paddle manufacturer's name, with black tape. I hoped my efforts would pay off.
I paddled slowly and consistently with no sudden movements. Consciously, I tried to minimize the sound of the water dripping from my paddle. Unconsciously, I was probably holding my breath. Finally, when I got to the sunny side of the bird, I quietly stowed the paddle and silently drifted to my photographic nirvana.
The little hawk ignored me. It spread its feathers wide and continued to soak up the sunshine. Both of us were obviously pleased with our locations, however, I had a growing sense of discomfort. Every feather on this bird's body seemed to be at least partially erect. The feathers were held out to apparently maximize their exposure to sunlight and air. The normal queues which I use to guess the bird's species were all in an unfamiliar state. Even though I loved the bird's wide-open feather display I was feeling uncertain about my ability to determine if this was a Sharp-shinned or a Cooper's Hawk?
These two small accipiters are very similar. The juveniles of both species have dark vertical streaks, sometimes shaped like teardrops, on their chests. At the very least, I could be certain it was a young accipiter.
A few days later while walking along the north side of Montlake Cut, a person, a few yards in front of me, startled a hawk which was evidently hunting along the crest of the ivy-covered hillside. I saw the flash of movement as the bird rose up from the ground and settled on an eye-level branch. I stopped immediately and quietly adjusted my camera.
This bird was not relaxing in the sunshine. Its feathers were all in their 'normal' positions. It was alert and looking all about, clearly hoping to return to the hunt. In this case, I felt fairly certain it was a Cooper's Hawk. The legs looked relatively stout, unlike the skinny little legs of a Sharp-shinned Hawk. Plus, the profile along the back of the head had a break, e.g. a visible change in direction, at the crown of the head. With Sharp-shinned Hawks, this profile is normally one smooth, unbroken line.
I did not attempt to get any closer, however, I did shift silently to my right hoping to line up some yellow leaves behind the bird's head. At this angle, the profile no longer shows any break. The Cooper's break is not always visible, but it is still useful field mark.
As the bird turns just a bit further we can see the hint of a break once again. I am not sure what the hawk was hunting. I have often seen Dark-eyed Juncos in this area. Last summer, I watched one of the Montlake Cut Bald Eagles fly to the nest with a rat it caught just below this spot. Northern Flickers also frequent this area. All of these would make a nice meal for a young, hungry accipiter, excluding the eagle of course.
Another clue I sometimes utilize is the 'barrel-shaped' body of a Cooper's Hawk versus the chesty, 'padded, football-player' shape of a Sharp-shinned Hawk.
Of course, when the bird momentarily puffed-out its feathers the definitive body shape became a bit obscured, still this bird looked more 'barrel-shaped' to me.
The person who startled the hawk was also a bit surprised by the bird. After watching the bird for a few moments the person continued on his way. The hawk appeared to refocus on the last known location of its prey.
Without any nearby distractions, the hawk returned to the hunt.
It landed near its original position. I was not a surprise to see a Cooper's Hawk hunting close to the ground. On the ground, they remind me of the velociraptors depicted in movies. I am sure glad Cooper's Hawks are not six foot tall. Apparently, its prey had scurried away or found a nice place to hide.
Just before the hawk gave up and flew to the south side of The Cut, it gave one last look over its shoulder. It seemed as if it was hoping the prey might try to sneak out of hiding as soon as the bird turned its back.
With the first bird in this post, there were numerous little hints, including the break in the profile, which made me thing Cooper's Hawk (COHA). Still, wondering what I did not know, I decided to ask the opinion of Martin Muller, from the Urban Raptor Conservancy (URC). First, I visited their comparison of the two birds on their website. Click Here to read their thoughts and view the examples.
After working through the hints I still had a few questions. Essentially they were:
1) Tail - This bird clearly has a rounded tail when spread. This makes me think COHA, however, the graduations in tail feather length seem a bit less than 'normal' for a COHA, to me. But the general look at the end of the tail is rounded.
2) Legs - I really struggle to see this difference. This bird's legs look a bit gnarly to me, but still rather thin. I lean toward COHA.
3) Head and Eyes - Hard to judge with all the feathers erect, but the eyes certainly do not look large, which makes me lean slightly toward COHA....
4) Streaking and Underparts - In the first photo, the streaking extends lower like a COHA. Thank you! This is a brand new clue for me to consider.
Martin's reply put me at ease.
"Larry,
I will go with your gut and call it a Coop.
I mean, look at that spread tail!
And the "smallish" eye forward of center in the face.
The streaking on the lower breast.
The leg diameter and therefor relatively shorter looking toes.
All those things you said...
...Martin"
It is wonderful to get an expert opinion. I always learn something.
Among other things, I had been uncertain about the minimal variation in the length of the tail feathers. My photos, which Martin used on the URC website show more variation in feather length for the young Cooper's Hawk. I now have a more refined standard to judge by.
I also came across another interesting field mark in Peter Pyle's, 'Identification guide to North American Birds'. He mentions that the white tip of a Sharp-shinned Hawks tail feather is usually 4mm or less, which on a Cooper's Hawk it is usually 4 to 11mm. For those who think in inches, this translates to roughly 1/8 of an inch and nearly 3/8s of an inch, respectively.
Clearly, this sun-drenched accipiter has the larger white tips on its tail feathers.
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