Tuesday, December 20, 2011

John Blakeman on the Snowy Owl Irruption and Another Typically Mysterious Accipiter- Cooper's or Sharp-shinned?

I looked out, and WHAT? There is now yet a different Accipiter haunting my backyard? This one is quite a bit smaller and has the cheek to sit on the birdbath.

And why is it that whenever I see an Accipiter, the tail is obscured? Note the end of the tail, considered a definitive field mark, rounded for a Cooper's Hawk and straight across for a Sharp-shinned, isn't in view.

The tail tip isn't in view here either. Though compared with the previous sighting which was very likely a Cooper's Hawk, not only is this bird smaller but the head appears rounder.

According to Peterson's Field Guide to Hawks of North America, Sharp-shinned Hawks rarely raise their hackles (the feathers on the back of their heads) whereas Cooper's Hawks very often sit around with their hackles raised.

Eventually "he" made a break for the House Sparrow's twig pile without any luck as far as I could observe as he took off before long having likely seen me lurking behind the glass.

Anyone feel confident in making a definite ID?
I'm leaning towards a Sharpie this time.

And next up, an essay from John Blakeman concerning ""real" rural Red-tails and the recent Snowy Owl irruption landing many in the U.S.


You've noted the extreme wariness of rural RTs in regard to humans. I marvel at the lackadaisical attitude NYC RTs have toward humans, with whom they pay so little attention. Not so with our "real" rural red-tails.

Also, the RT sitting on the wire was, typically, an immature (told by it's slightly longer tail). Haggards almost never park themselves out on such thin wires. But hungry immatures, as your photos show, will do this.

I sent a long discourse to Marie Winn on snowy owls, for posting over there; but she's in China, so it won't go up until next week, perhaps.

As you may already know, there is a massive irruption of snowy owls invading the US from arctic Canada. I'm sure there have been many spottings in Wisconsin already. Many have been seen crossing at Sault Ste. Marie, MI, and we've got a bunch of them here in N Ohio that have crossed 50 or 60 miles of open Lake Erie.

Most are immatures, indicating that there is a lemming high in the arctic. That caused massive reproduction last spring, with up to 10 to 12 hatched owlets per nest. Now, those yearlings are starving in the arctic winter, so they are flying south. Most will never make it back to the arctic by next spring, as hunting voles down here is harder than finding abundant lemmings up there.

Adult snowies can handle the more difficult hunting conditions of the winter, so they stay up there during a lemming population high. But alternately, in a lemming low, there are few immatures that are produced, and many adults begin to starve and fly south in winter. If there lots of immatures in the irruption, as now, it's a result of massive spring reproduction, which resulted from a lemming population high.

But if the irruption is mostly adults, that indicates a widespread lemming low. Even many of the adults, then, begin to starve and are motivated to fly south in search of winter food. That may be the case in 3 or 4 years, when the lemming population curve reverses.

--John Blakeman

Thank you, John, for the essay and also for the RT gender and age ID from the previous posting. It will be very interesting to see how the unusual current lack of snow in much of the Midwest will affect the hunting of the visiting Snowy Owls.

There is no doubt an irruption in progress, but I suspect the lack of snow may be helping to contribute to the many human sightings during this one.

I've not had a close encounter with a Snowy Owl this year as yet, but several decades ago I saw my first fly out of a snowy field in Wisconsin, a scant half dozen feet from my windshield as I parked the car on the verge for another reason and accidentally flushed it. My jaw dropped and stayed that way until it disappeared beyond the horizon. They are stunningly beautiful birds.

Donegal Browne

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