Saturday, July 21, 2012

More From the Fabulous Fifth Avene Fledglings plus John Blakeman on Red-tail Vision

Photos and italicized commentary by our man in the field Jeff Johnson.  Un-italicized commentary is mine.

We're picking up from yesterday on the Fifth Avenue Fledglings with Flare on the Fourteenth of July.  Opera Star was perched in a tree taking his ease in his father's favorite stance when his sister appeared on the ground and began doing a little twig killing beneath him.

Opera Star leans over and gives her a look, possibly considering as fledglings do, a little surprise attack and tussle with a sibling perhaps? .

Fledge continues to play hunt all about the area under the trees. Metadata time 1828.
 Opera Star gives the "fledge look" to something off to the NNW. Metadata time 1829.
 Opera Star finally leaves his perch. Metadata time 1834.
 The two fledges we've been observing have flown into the NNE Cedar Hill trees. Metadata time 1835.
 Red-tail streaks in low-level diagonally across Cedar Hill from the SSE. Metadata time 1836.
 Fledges watch this very closely. Metadata time 1837.
 Red-tail continues this low-level airshow as fledges watch. It must be a parent, but I can't tell which one or if anything is being carried. Metadata time 1838.

Interestingly the tail on the above hawk appears brown in the photograph but sometimes modern cameras "make decisions" about the fact that the rest of the body is a certain color and if tail color isn't clear  they "make it match". 

It was a food drop and one of the fledges has something mantled in a lower tree limb at the top of Cedar Hill without my having gotten any frames of the actual drop (once more !).  Metadata time 1839.

Don't feel too bad Jeff, I've been taking pictures of Red-tails in breeding season since 1995 and I've yet to get "the shot" of a drop either. 
 Fledge begins eating. Metadata time 1839.

 This fledge watches the other have dinner from a tree seventy feet to the west. Metadata time 1840.

 Mantled fledge eating seen from ENE. Metadata time 1841.
 Less guarded now, the fledge continues to eat (seen from west). Metadata time 1844.
 927 Nest check from near the Sailboat Pond. No one visible. Metadata time 1851.

Remember when Opera Star when Opera Star leaned his head in one of Jeff's photographs and I said that, Red-tail expert John Blakeman originally explained what was going when Charlotte, mate of Pale Male Jr.  did the same repeatedly while sitting the nest on the Trump Parc?

I asked for an encore of  his explanation and he, as always a major help in these matters, sent it along spritely.


I haven't seen Jeff's photo of an immature looking up into the sky, but the only reason this is done is to observe a bird above; usually some hawk or other raptor.
In the hot weather of late, RTs and other hawks can ascend on a thermal (many miles away) and be at 5 to 10 thousand feet in a few minutes. It's never 95 degrees at those altitudes, and RTs can simply lock their wings and soar effortlessly (and cooly) up there for hours, unseen by virtually anyone on the ground, except for another Red-tail.
Red-tails will peer up at other raptors soaring above, particularly peregrines. They pay little attention to Cooper's hawks or kestrels up there.
Often the Red-tails will be seen looking above with their heads tilted to the side, as though they were looking out of the side of their heads, with one eye, not straight forward. That's because hawks have two foveas in each eye, areas of highly concentrated light-receptor cells. We humans, and most animals, have a single fovea right at the back of the eye, allowing us to see in detail in the central area of vision straight ahead. But the most concentrated light-receptor cells in the retina of a hawk is not at the back of the eye, but on the side. So, when a Red-tail is seen apparently looking out to the side, but with one eye angled up into the sky, it's looking at something in the great distance, using but one eye, with the image focused solely on the secondary (but more detailed) fovea.
People unfamiliar with this are easily confused about what a hawk is looking at when the head is tilted to the side, with one eye angled into the sky. Makes no sense to those of us who can use only the foveas at the direct rear of our eyes.
I have some fun watching this in my falconry Red-tail in October here along the south shore of Lake Erie in Ohio. Lake Erie is wide, so migrating Red-tails and other large hawks elect to skirt around the western end of Lake Erie, between Detroit and Toledo, instead of trying to fly 50 miles or so across the water. So, all of the migrating raptors going south out of the counties of Ontario on the north shore of Lake Erie get concentrated as they fly around the western shore of the lake.
Once they get past Lake Erie, they simply head straight south, pretty much following I-75. So, I've often had my falconry Red-tail on my fist, beneath this stream of hawks passing overhead. In a quick scan of the sky I can see nothing but blue (or gray -- more likely) sky. But my hawk is tilting her head right and left, keeping track of the migratory hawk traffic above.
I've learned where she's looking when she tilts her head, so I can point my binoculars right where she's looking. And, sure enough, there will be a hawk or two in that field of vision.
Quintessentially, Red-tails are visual creatures, facilitated by not one but two retinal areas of intense light-receptive cells.
--John Blakeman
Happy Hawking!
Donegal Browne 

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