Prairie Falcon Ages

posted by Jerry Liguori at
on Saturday, January 18, 2014 

Just want to post a few pics because of a recent discussion on Prairie Falcon ageing. Sometimes it's not so easy to tell the age of a Prairie Falcon since the juvenile and adult plumages are very similar to each other. Flesh parts (cere, feet, orbital ring) on the larger falcons (Prairie, Peregrine, and Gyrfalcon) turns from pale bluish to bright yellow, but the time it takes for these parts to change color varies quite a bit, and in Gyrfalcon, it takes longer to change than in Prairie and Peregrine. In fact, oddly, many juvenile Peregrines have yellow feet (but often not ceres) by early fall. Also, the flesh parts of males tend to change quicker than on females, same with eye color of accipiters, but of course this varies somewhat individually. By the way, Prairie Falcon gets its adult plumage the first time it molts in its 2nd year.

There are plumage differences between juvenile and adult Prairie Falcons, and often it is easy to see, but sometimes it is extremely confusing. Juveniles typically have short streaks on the underbody, where adults have more rounded spots. The head on adults is more finely streaked than the plainer brown head of juveniles, and the pale spots on the back of the head are less white. The upperwing coverts have broader buffy tips, and the secondary and primary coverts are more heavily barred an adults than on juveniles. The tail of adults usually shows more complete bands looking paler overall than on juveniles.

Here are some composites of juveniles on the left and adults on the right (note how similar the two ages appear), and a head shot of a juvenile in September that is already changing color on the cere ('click' to enlarge). 
Blogger Brenton Reyner said...

Great post Jerry! I'll keep my eye out for these features in the future.

January 18, 2014 at 5:23 PM  
Blogger Jerry Liguori said...

Thanks Brenton, it can be a confusing issue without knowing what to look for

January 18, 2014 at 6:15 PM  
Anonymous Ron Dudley said...

Jerry, For me personally this is an especially valuable post. In the past I've confused the age of Prairie Falcons in particular in my blog posts - in fact you may remember pointing that out to me in a private email once (which I appreciated very much). I'll be bookmarking this one, for sure.

January 19, 2014 at 6:29 AM  
Blogger Jerry Liguori said...

Your always humble Ron!

January 19, 2014 at 7:23 AM  
Anonymous Hatem Gomaa said...

Does that eyebrow seem shrter in the adult also? And it looks like the light edge color of most of the dorsal feathers is lighter and orangier on the adult than the juvy?

BTW, Jerry you mentioned the prairie falcon in your raptor on raptor experience twice, remember? And do you remember that video we talked about with this falcon hunting ducks?
This bird is really underrated for the prolific hunter that it is. And I wouldn't doubt that if it really wanted or needed to, it could attain great speeds similar to the peregrine. It just hasn't been studied or observed as closely as the peregrine for obvious reasons, but this bird is truly one of the most incredible aerial hunter and flyers. Would you agree?

January 19, 2014 at 9:42 AM  
Blogger Jerry Liguori said...

Yes, the eyebrow differs for the most part but nothing is 100% so be careful I guess.

Definitely give the Peregrine a run for its money...

January 19, 2014 at 12:25 PM  
Anonymous Hatem Gomaa said...

You know, I forget where the term originated from, but it was more associated with the gyrfalcon and maybe it was given to the bird during the early times of falconry when the sport was first invented, but the term referred to the gyrfalcon as the "bearded falcon" because of that puffy group of feathers right after the lower mandible near he throat and the bottom photo is a beautiful representation of that feature. Look at that beard! It's exactly where the name came from but interesting to see it on the prairie.

January 19, 2014 at 3:43 PM  

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