Updated: Mar 25
Several years ago, a white hawk was documented in central Wyoming. To protect the bird from nefarious activities, a group of interested parties have 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.
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 (RTHA) or Swainson's Hawk (SWHA)? 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.
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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 RTHA would not move 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 utilizing second-hand information. Though, its mate's identification might not be helpful, as I have 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."
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 RTHA and SWHA, and typically RTHA have thicker toes and tarsi. Even the smaller ssp 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 RTHA. This bill is TINY compared to a RTHA. A tiny bill is what gives the SWHA the "cuter" face appearance. Now, we cannot measure bill length in photos, but regardless of that measurement, the cere is too extensive. In SWHA the cere is expansive. In RTHA, the "keratinized" portion of the bill is more expansive than the cere. This clearly leans toward SWHA. Additionally, the "hook" on the tip of the bill? Sharply curved and thin. This is indicative of SWHA.
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2A) I noticed a new helpful trait today while combing through photos of RTHA and SWHA. The leading edge of the cere on a SWHA does not meet the under-nares feathering. On the RTHA, the leading edge of the cere appears to angle backwards, 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 SWHA. While not exclusive, RTHA do not hunt from the ground or low perch as frequently as SWHA. 60-80% of RTHA hunting is done from an elevated perch. This alone does not exclude RTHA, but the behavior is more unusual for RTHA.
4) Facial Feature - The furrowed brow on this bird is more extensive than expected from a RTHA. This is anecdotal, but it still gives the GISS I've come to expect from SWHA.
5) Feather Shape - The outer primaries are highly tapered and fine. RTHA 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 RTHA without pink feathers. Albino, yes. But our bird is not albino.
7) Primary Projection - This is the best evidence for SWHA. And it would be very hard to dispute it. This birds wings are longer than its tail. Very FEW to no calurus (RTHA subspecies) or kriderii (RTHA subspecies) exhibit this. Wings longer than a tail indicate a longer distance migrant, ie SWHA. 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.
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 4 years of defending my position.)
See more photos below!
I would like to add a clarifier 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 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 from 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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