Gary Davidson of Nakusp, B.C. is an old friend and is familiar with my passion for Red-tails. This winter he captured an image of a Krider's Red-tailed Hawk that was hanging around the Davidson's RV in McAllen, Texas. You think our Red-tails can be pale in the Okanagan/Thompson? Take at look at this bird:
 |
| 1. Photo by Gary Davidson - Krider's Red-tailed Hawk - McAllen, Texas- late Feb. 2013 |
This is an immature Krider's Red-tailed Hawk. Aging marks include the poorly developed dark border to the trailing edge of the wings, the multiple barred tail, the pale eye, and the pale panel near the end of each wing.
Why is this bird a Red-tailed Hawk at all? The dark markings just behind the leading edge of the inner wings are called patagial marks. Patagial marks are a diagnostic feature of Red-tails. Compare this bird with the light juvenile Ferruginous Hawks pictured on page 385 of Brian Wheeler's indispensible Raptors of Western North America (Princeton 2003). Also take a look at Dunne, Sibley, and Sutton's excellent second edition of Hawks in Flight (Houghton Mifflin Harcourt 2012) pages 76-77 to note that a light juv. Ferruginous may show something like a patagial mark though the marks are slightly farther towards the inner wing and more distant from the leading edge. You'll also want to look at the new Crossley ID Guide - Raptors by Crossley, Liguori and Sullivan (Princeton 2013).
Here's an image taken by well-known Kamloops naturalist Rick Howie of an immature Red-tail in the Kamloops area. It shows a large dark patagial mark, the pale window panel typical of an immature, the light eye (not quite so reliable as an indicator of age, I've read), and the many barred tail, plus a couple of other features worth looking at.
 |
| 2. Photo by Rick Howie |
 |
| 3. Photo by Chris Siddle - Westwold, B.C.- July 2010 |
Let's go back to Photo 2. When classifying Red-tails I always look at the breast first to note what the background colour is, in this case obviously white, and whether it is streaked or not, and how heavily. In this case the breast is unstreaked. Then I note the heaviness of the belly band and its width. The bird in 2. has a dark belly band on white underparts but the band doesn't appear particularly wide. Next comes the colour of the underside of the tail and the width and number of tail bands. That leaves us with undertail coverts, the tarsus and the head and throat which all appear quite "normal" in this case of Photo 2.
Here is another image from Rick Howie.
 |
| 4. Photo by Rick Howie, 21 April 2013, Kamloops |
What differences do you spot between the immature in 4. and the immature in 2? The most obvious difference is that 4. has a broader, more solid dark belly band. Noting individual differences such as this will help the birder keep track of the Red-tails around him.
I am ending this post with a summary of Red-tailed Hawk reproduction because I would like to encourage my readers to become familiar with the species beyond identification. I relied upon Charles R. Preston's book, Red-tailed Hawk (2000, Stackpole Books, 5067 Ritter Road, Mechanicsburg, PA. 17055.) for most of the information.
Nest Selection: The pair selects a nest site up to 3- 5 weeks before the female lays eggs. Nest sites in the North Okanagan include groves of cottonwoods and coniferous trees in or on the edge of forest. Nests are large piles of sticks often from the tree that the birds have chosen to nest in. Nests can be difficult to locate or very obvious.
Eggs and Incubation: The female usually lays an egg every other day. A complete clutch ranges from 1 to 5 eggs, with an average over North America of 2-3 eggs per clutch. Incubation is by both male and female, but mostly female, and commences with the laying of the first egg. The male provides food for his mate, but she may also hunt for herself. Incubation to the hatching of the first egg may be as short as 28 days though the period may extend as long as 35 days since hatching of first to last laid eggs may occur over several days. The first chick to hatch has the developmental advantage and siblicide is known.
Nesting period: lasts from 39 to 46 days.
Fledglings: have to learn to fly well, and at first beg incessantly, a well known sound of June and July around Vernon. This period when the fledglings are variously dependent upon the parents can last weeks, if not months.
To leave comments about this or any of my other posts, contact me at chris.siddle@gmail.com
I am ending this post with a summary of Red-tailed Hawk reproduction because I would like to encourage my readers to become familiar with the species beyond identification. I relied upon Charles R. Preston's book, Red-tailed Hawk (2000, Stackpole Books, 5067 Ritter Road, Mechanicsburg, PA. 17055.) for most of the information.
Nest Selection: The pair selects a nest site up to 3- 5 weeks before the female lays eggs. Nest sites in the North Okanagan include groves of cottonwoods and coniferous trees in or on the edge of forest. Nests are large piles of sticks often from the tree that the birds have chosen to nest in. Nests can be difficult to locate or very obvious.
Eggs and Incubation: The female usually lays an egg every other day. A complete clutch ranges from 1 to 5 eggs, with an average over North America of 2-3 eggs per clutch. Incubation is by both male and female, but mostly female, and commences with the laying of the first egg. The male provides food for his mate, but she may also hunt for herself. Incubation to the hatching of the first egg may be as short as 28 days though the period may extend as long as 35 days since hatching of first to last laid eggs may occur over several days. The first chick to hatch has the developmental advantage and siblicide is known.
Nesting period: lasts from 39 to 46 days.
Fledglings: have to learn to fly well, and at first beg incessantly, a well known sound of June and July around Vernon. This period when the fledglings are variously dependent upon the parents can last weeks, if not months.
To leave comments about this or any of my other posts, contact me at chris.siddle@gmail.com
