Ageing Adult Red-tails by Tail Bands?

posted by Jerry Liguori at
on Saturday, January 4, 2014 

I've received several emails asking me whether Western Red-tailed Hawks in their first adult plumage have multiple tail bands, whereas older adults have unbanded tails. I asked where that notion came from? It turns out it's published in the 2008 Pyle guide. I wish it were that easy, but the truth is that tail patterns of adult Red-tails of every age vary from being completely banded to unbanded. Before we look at examples of this, let’s dissect the issue. First, I'm curious how this was determined? What specimens or live birds were reviewed? There are millions of Red-tails out there, so a very large sample size from a broad geographic range is required to make such a statement. Is this proposed tail pattern true for dark and light-morph birds? How about males and females? Why were the other races/types of Red-tail that show tail bands not treated or commented on? Also, can we review the study birds to fact-check the identifications to race, or was that assumed? These type of questions should be posed for any study. The statement about tail bands just seems arbitrary and poorly researched. If there’s one thing I’ve learned, it's to question things you read or hear until fact-checked, as there are inaccuracies in literature that have been propagated over the years, even in texts written by the 'top experts.' It is impossible to reach the entire birding community to fix a mistake once it's published. Everyone makes mistakes, but I find it irresponsible when authors publish theories and assumptions as fact that results in misinformation ingested by the birding community and thereafter very difficult to purge. Have you ever discussed an ID with someone where you had facts to support your stance, but their stance was "so-and-so said so?" I hope the younger generation of birders gets on-board with taking the time to research things properly and publish only what is supported with real data and verifiable examples.

I think it's the responsibility of all birders to share information if it corrects an error. However, it's also requisite to be absolute before attempting to challenge literature. A friend sent me a few excerpts from the Red-tailed Hawk section of the Pyle Guide and I was horrified at the misinformation in there -- to see so numerous mistakes in one species account is alarming! If one of North America’s commonest birds is poorly treated, I cringe to think of the validity of the other species accounts. Here's one I wasn't even aware was in the Pyle guide: I will address the inaccuracies in Red-tailed Hawk section in various blog posts since there is not enough room here to do it, as well as problems with other raptor species throughout Pyle's Guide so birders are aware of them. Hawk banders especially need to use caution since they are responsible for the data they submit to the BBL. If you smell a rat, "Unknown" for age/sex is proper and always acceptable.

Check out these Red-tails in their first adult plumage (labeled 2nd-year) that lack multiple tail bands, and various others at least one year older (labeled After-2nd-year) with obvious tail bands…and thanks for reading. By the way, if you want to age Red-tailed Hawks correctly, note either retained juvenile feathers (preferably flight feathers) for SY/TY, or 2 generations of adult feathers for ASY/ATY. Sometimes it is possible to age buteos as 3rd or 4th-year in fall, but that is difficult without extensive practice, and sometimes inaccurate in certain cases. Eye color can be helpful as a hint (and does match up well on the birds below), but NEVER takes the place of flight feather ages. And remember, NEVER age adult Red-tailed Hawks based on presence/absence of tail bands! 

 At least 8 years old (known nester)
 After-3rd-year (aged after January 1st)
 At least 12 years old (known nester)
 At least 11 years old (known year-round resident)
 At least 6 years old (known nester)
Anonymous Derek Lyon said...

Very interesting post, thorough and lots of nice photos that make your point.

January 5, 2014 at 7:35 AM  
Anonymous Hatem Gomaa said...

What a terrible "assumption" on their part. And that's exactly what it is, an assumption which is the furthest thing from stout, thourough, field researched conclusions. To say that western red-tails that go into their first molt and that exhibit full bands on their tails will end up being adults with lesser or no bands at all is like saying the rusty red tail will become purple as the bird gets older!? Or that some of the other color patterns will change with age. There's absolutely no basis to that and it's particularly tricky to do that with western red-tails because of the incredible range of plumage variations compared to most of the other sub-species. Obviously they didn't base that on any substantial research or else they would've found out there is no truth to such a thing. And that's the problem with any publications of any kind. Anyone who has the financial means to get a publication put out can basically say anything and naturally there's no regulation of any kind when it comes to published "supposedly researched" information. The onus should be on the publisher to be sure that they list some sort of disclaimer that the material published is strictly the opinion/information of the author based on his/her research and leave it at that. It's a tough call.

Good looking out on your part, Jerry. I'm amazed at the width of the dark sub-terminal band on the RT in the 10th photo down. That is really incredible. And then you also have banded or barred upper-tail coverts on the birds that have heavily banded tails. The outermost row of the coverts seems to have the same characteristics as the heavily banded tails and it looks (to me, at least) that the heavier the banded tail is, the heavier the barring on those outer upper-tail coverts seem to be. I'm sure it's not definitively that way all the time, but seems somewhat consistent. You can see that on the RT in the 4th photo up from the bottom. That tail is simply spectacular with all the banding and variations of rust and browns and even some greys.

January 5, 2014 at 7:51 AM  
Blogger Jerry Liguori said...

Hi Hatem

The thick sub-terminal is another post I will discuss, seems there is some confusion in the literature on what that suggests. But its something I've looked at since the late 80's and have lots of data on.

More to come...

January 5, 2014 at 8:42 AM  
Blogger Jerry Liguori said...

Thanks Derek!

January 5, 2014 at 8:42 AM  
Blogger mike said...

Well reasoned, well stated, and well supported by photos. I agree with you for those reasons, and from my own experience banding and aging large numbers of RTHAs in the western US.

January 5, 2014 at 9:13 AM  
Blogger Jerry Liguori said...

Thank you Mike -- I hope to share more in the future, and I'm glad you saw this on your own! I hope every bird bander is made aware of inaccuracies for the sake of legit data.

January 5, 2014 at 10:18 AM  
Anonymous Jon Ruddy said...

I just visited your blog and boy am I ever glad that I did! Nice post on Red-taileds; great pics. Can't wait to pour another cup of coffee and enjoy a good study.


January 5, 2014 at 11:04 AM  
Blogger Mia McPherson said...

Jerry, you never fail to educate me.

January 5, 2014 at 11:33 AM  
Blogger Caitlin Davis said...

It seems like a no-brainer, as someone who has seen many Red-tails in hand, but most people don't get their information the same way. We can't blame them for believing peer-reviewed work, but how do we go about correcting it? Blogs like this help! Thanks Jerry, keep them coming!


January 5, 2014 at 11:51 AM  
Blogger Thomas Dixon said...

I'm admittedly a beginning raptor biologist, and have probably learned more about raptor identification from your field guides than any other source, but feel the criticisms aren't really warranted given Pyle's caveats and suggested use of his guides.

He notes that a synthesis of traits should always be used when making any determination and a caveat is even included in the figure on ageing tail bands that reads "Note there is individual variation within all subspecies/age groups; typical examples are shown."

Exactly what he means by "typical" in a quantitative sense is I'm sure something that we'd all like to know, but from my understanding, I think his claims are valid.

Jerry, I'm sure you have a huge number of photos of known subspecies and age that show the dorsal tail surface. Perhaps an analysis of these would help us get a better idea of the truth?

January 5, 2014 at 12:22 PM  
Blogger Jerry Liguori said...

Hi Thomas

Glad you have my books and use them, it is nice to hear. Just wanted to say, I'm not criticizing Pyle, I just wanted to clear an issue up since a bunch of raptor watchers and banders have asked me about this over the past few years. Publishing that information with a diagram makes it significant and people are not going to know what to use as a caveat and what not to. To say ""there is individual variation within all subspecies/age groups; typical examples are shown." is totally misleading, erroneous, and irrelevant after the fact. He probably should be clearer in his book. Or better yet, research it more properly. If he thought it was useless and variable he wouldn't have and shouldn't have published it in the first place. But it is clear now, and that is the point of the blog post. I think I am fair in my post, and I show many examples in the photos. My feeling is "If I have information, do I keep it to myself?" And the answer will always be NO and should be NO.

I appreciate you opinion, and that is the truth

January 5, 2014 at 1:06 PM  
Anonymous Bryce Robinson said...

It's been so frustrating for me as a young Raptor Biologist to try and convince people that what I'm showing them on live birds is evidence enough that what the Pyle guide says is not correct. It has happened multiple times, and with multiple species.

I'm really glad you posted this. The figure in the Pyle Guide that supports this RTHA tail banding assumption caught my eye last year. I immediately knew it was incorrect, and I couldn't understand why it was included in the first place. I've struggled with folks since then trying to convince them that you cannot age a Red-tailed Hawk using the amount of banding in its tail. Now I'll have something to show them, which bolsters my own photo evidence. I hope Pyle sees the simply as an opportunity to revise his guide. With such limited resources for the hawk banders to use, the Pyle guide's positive reputation has made it a go-to resource. For the BBL, this is a bit problematic, as it taints some of the data of population distributions and demographics that are the sole purpose of the banding effort. I see it as my responsibility, as everyone that bands birds to use the Pyle Guide as a reference but not as a stand alone source.

January 5, 2014 at 1:47 PM  
Anonymous Marc Grieco said...

Jerry, please share things like this, it may be uncomfortable to correct someone, but that's how bird watching and bird ID evolves and moves forward. I think every birder wants to have the most current information. Your blog is unique in this way. Kudos!

Look forward to more posts.

January 5, 2014 at 3:00 PM  
Blogger Jen Hajj said...

Nice info, as always, Jerry.

January 5, 2014 at 6:21 PM  
Blogger Jerry Liguori said...

Hi Jen!!!

it is great to hear from you, glad you like my blog and hope you drop in more often.

January 5, 2014 at 6:25 PM  
Anonymous Ron Dudley said...

I loved this post, Jerry. You're reasoning is logical and supported by great images. Very well done!

January 6, 2014 at 6:06 AM  
Anonymous Hatem Gomaa said...

I don't think the tail bands are similar to tree growth-rings where you can count the rings and figure out how old the tree is! And unless you perform extensive research that would probably take a decade or more and sample 20,000+ individual birds and tediously recording the pigmentation of each one…then it's just not feasible, actually impossible, to make such a determination. There are so many other factors that could be included in that list. I don't even think it's possible to make a determination that a bird is older than another (and not necessarily determine its accurate age) simply because it has fewer bands. How could one possibly make that determination without having witnessed the aging process of countless birds to see that older ones used to have more bands when they were young?

January 6, 2014 at 9:00 AM  
Anonymous Anonymous said...

Excellent examples, and all nice birds to look at. Thanks for sharing this.

January 6, 2014 at 10:55 AM  
Anonymous Kyle C. said...

I think birders and banders would know better not to age these birds by the tail banding. If they can see the 2 ages of wing feathers, they would use that instead, I hope at least. But being in a book, I for one agree completely with why you would point it out, publishing this type of thing would only confuse people when they see the contrary.

January 6, 2014 at 11:05 AM  
Anonymous Anonymous said...


I like these examples of ages, I can test myself to see if i can age them correctly by the wing molt, and I passed! I enjoy when you talk about the nitty-gritty of hawks.

January 6, 2014 at 7:36 PM  
Anonymous Pete Gustas said...

Jerry, you are ackowledged by the birding community as a raptor expert, therefore, pointing out something that is confusing to birders is a service to us. I hope you continue whenever you become aware of these problematic issues.

January 7, 2014 at 7:51 AM  
Anonymous Hatem Gomaa said...

Looking forward to your post on the width variations of the sub-terminal band, Jerry.
I'm not even aware of any literature out there regarding what it suggests but would love to hear what it is and what you have learned from your data. Sounds like possibly another correction coming soon? :)

January 7, 2014 at 8:29 AM  
Blogger Jerry Liguori said...

Yes Hatem -- I studied Eastern and Western Red-tails in-hand from 1989 - 2001 and found some conclusions on the width of the sub-terminal band.

January 7, 2014 at 8:37 AM  
Anonymous Anonymous said...

Jerry, I applaud you for post slike these. I read the Pyle guide and am completely confused by sections and find myself questioning the truthfulnees of some things in there. Your pictures here are much more representable to ages than a diagram and are ideal for future reference. Can I email you privately with questions I have pertaining to Pyle's guide?

January 10, 2014 at 11:34 AM  
Blogger Jerry Liguori said...

Of course you can email me, I'm always happy to answer questions if I can, and address some of your concerns, but I will be happy to have you remain anonymous of course if I post them on the blog. My email is on my contact page.

Thanks for the comment, and glad to see you are looking at things critically

January 10, 2014 at 11:37 AM  
Anonymous Q. J. said...

You definitely make a clear case for not using this feature as a way to age Red-tailed Hawks. Great post! Looking forward to you other eye-opening clarifications.

January 15, 2014 at 9:55 AM  

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