White Hawk - A Leucistic Red-tailed or Swainson's Hawk?
Several years ago, a white hawk was documented in central Wyoming, about two hours from Flocking Around HQ. To protect the bird from nefarious activities, a group of interested parties has decided to keep its exact location hidden. This is its ... ID story.
Let me preface this post by saying I am a major bird nerd. I am part of 10+ bird/birding Facebook groups and email lists. However, I rarely partake in identifying photos of birds for other people. I help when I am asked, but otherwise, I avoid adding my thoughts to bird ID questions from photos. This is one of the few times where I offered to gasbag on a bird.
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When this hawk came to my inbox in 2016, it introduced a challenge for me. I needed to identify a hawk without using "field marks." The original (and subsequent) photos showed no markings on the wing and tail. The habitat was not conclusive. No mention of voice was offered. Was it a Red-tailed Hawk or Swainson's Hawk? When I opened the photos up originally, I made a snap decision. Why? The GISS (general impression of shape and size) of this bird shouted to me. These were the first photos of a 'leucistic' Swainson's Hawk that I had ever seen.
Learn more about the differences between leucism and albinism here!
Background Information on this Leucistic Hawk
I have received photos of this bird every year, for the past 4 years, during the second and third weeks of April. Now, does the bird show up before then? Possibly! However, we should not depend on the date as a sole identification factor. Especially since Swainson's Hawks are regularly showing up by the second and third weeks of March in MT, SD, ND, ID, etc. Additionally, has this hawk been documented past the first week of October? Seemingly, no. A Red-tailed Hawk would likely not migrate until much later in the season (presumptive by me).
Originally, I was told by an observer that this bird was nesting with a Swainson's Hawk. Could they have been mistaken? Possibly! It can be risky to utilize second-hand information. Even if they were correct, its mate's identification might not be helpful as I had received no documentation of offspring... (that is an entirely different post on hybrids and when they produce young).
Let's get down to the nitty-gritty now, identification with a lack of "markation."
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Identification of white Red-tailed Hawks vs white Swainson's Hawks
1) Feet and legs - The toes of this bird are thin. As are the tarsi. I have banded Red-tailed Hawk and Swainson's Hawk, and typically Red-tailed Hawks have thicker toes and tarsi. Even the smaller subspecies have thicker toes and tarsi than this bird seems to exhibit in the photos.
2) Bill - Bill and cere length on this bird do not match Red-tailed Hawk. This bill is TINY compared to a Red-tailed Hawk. A tiny bill is what gives the Swainson's Hawk the "cuter" face appearance. Now, we cannot measure bill length in photos, but regardless of that measurement, the cere is too extensive. In Swainson's Hawk, the cere is expansive. In Red-tailed Hawk, the "keratinized" portion of the bill is more expansive than the cere. This clearly leans toward Swainson's Hawk. Additionally, the "hook" on the tip of the bill? Sharply curved and thin. This is indicative of Swainson's Hawk.
2A) I noticed a new helpful trait while combing through photos of Red-tailed Hawks and Swainson's Hawks. The leading edge of the cere on a Swainson's Hawk does not meet the under-nares feathering. On the Red-tailed Hawk, the leading edge of the cere appears to angle backward, and the under-nares feathering covers up the leading edge. I will test this on more examples and see if it pans out!
3) Perching Behavior - The photos of this bird frequently show it perched low or on the ground (it did not exhibit this behavior for me). This behavior favors Swainson's Hawks. While not exclusive, Red-tailed Hawks do not hunt from the ground or low perch as frequently as Swainson's Hawks. 60-80% of Red-tailed Hawks hunting is done from an elevated perch. This alone does not exclude Red-tailed Hawk, but the behavior is more unusual for Red-tailed Hawk.
4) Facial Feature - The furrowed brow on this bird is more extensive than expected from a Red-tailed Hawk. This is anecdotal, but it still gives the GISS I've come to expect from Swainson's Hawk.
5) Feather Shape - The outer primaries are highly tapered and fine. Red-tailed Hawk outer primaries are more "angular" or "truncate.".
6) Tail Color - There are no "pinkish" feathers in the tail. There are few to no photos of 'leucistic' Red-tailed Hawk without pink feathers. Fully albino, yes. However, this is 'leucisim' or partial-albinism.
7) Primary Projection - This is the best evidence for Swainson's Hawk. And it would be very hard to dispute it. This bird's wings are longer than its tail. Very FEW to no calurus (Red-tailed Hawk subspecies) or kriderii (Red-tailed Hawk subspecies) exhibit this. Wings longer than a tail indicate a long-distance migrant, i.e. Swainson's Hawk. Just look at the primary projection! Whoa! Peruse through photos of kriderii and/or calurus and you will rarely see a primary projection like that.
AND FINALLY...
8) Call - I waited 4 years to see this bird in person. Saturday I broke the end of my toe bone off and have been placed in a walking boot. Before the weekend ended, I ventured to see this bird, one-footed. As it left one of its perches, it did the only thing I needed to confirm its identification for any remaining doubters. It called.
Hellooooo SWAINSON'S HAWK!
(It would have been funnier if it called and turned out to be a Red-tailed Hawk. After four years of defending my position.)
Before you move onward to see more photos of this glorious bird, if you want to improve your raptor ID skills, I recommend snagging and reading THESE guides. They will improve your raptor skills!
The Crossley ID Guide for Raptors
See more photos below!
Swainson's Hawk Range Map
I would like to add a clarification to this post. The term leucism is often a very broad, all-encompassing term used by birders to describe white birds that do not have pinky eyes and skin. However, it may not be the correct term. While we have no geneticists on staff here at Flocking Around, we know a handful of geneticists.
According to some of these geneticists, rather than "leucistic," this Swainson's Hawk is exhibiting the physical characteristics of a bird with OCA4/SLC45A2. What does that random jumble of letters mean? Oculocutaneous albinism (OCA) involves the eyes, feathers, and skin of the affected organism, and OCA4 results from a genetic defect in the SLC45A2 protein that helps the tyrosinase enzyme to function. What does all that mean? It means this bird is exhibiting white plumage (obviously) and blue eyes, and this is the result of a genetic defect leading to a type of albinism. However, you are probably safest to just call in leucism. Or describe it as white. Or a hawk. Or a bird. The end. I think.
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