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Black Wing Tips

posted by Jerry Liguori at
on Tuesday, January 28, 2014 

I heard long ago that birds with whitish or pale primaries and secondaries have black tips to these feathers (not all do of course) because the melanin in the dark part of the feather helps to keep the feather structurally sound so they don't break or wear quickly. It makes sense and seems to serve that function so I never thought anything different, and it is a neat adaptation. Buy is it really true? If anyone has read otherwise, please write in and let me know. Here are some pics of birds ('click' to enlarge) with black wing tips…
Northern Harrier
Rough-legged Hawk
Ferruginous Hawk
6 Comments:
Blogger Bryce said...

I learned the same thing Jerry, though I don't recall where I read it. Melanin increases the strength of feathers, something that makes sense as the reasoning why many birds have barring throughout their flight feathers. I've also read that melanin production is costly energetically, which adds to the idea of barring, or stuttered melanin deposition. Keeping that in mind, why would some birds have less banding, why do particular species have dark flight feathers(SWHA), etc.? Anyway, I don't know if it is true in an evolutionary sense, like you ask, nor do I know how to test it. But, I do know that it is a very interesting and fun topic to explore.

January 28, 2014 at 11:30 AM  
Anonymous Derek Lyon said...

There're other long winged birds that mostly have black tips but others have none. Most gulls have black tips on there wings but some don't: Ivory Gull, Glaucous Gull and Iceland Gull. All are northern gulls and a black tip to its wings would make it stick out to predators.

January 29, 2014 at 12:41 PM  
Anonymous Matt said...

You guys are right, the pigment melanin strengthens the feathers and makes them more durable, and stiffer, which in my opinion is necessary for birds that hunt other animals. Not only is melanin found in the feathers, but its also found in the beaks and talons of raptors. Keratin by nature is soft and weak, which is why people are always breaking their nails on stupid stuff. by adding melanin to keratin, it creates a strong yet lightweight material that works for all raptors that need strength in places where its needed. of course nature breaks the rules and creates all white gyrs with no black, albino birds with no melanin at all in beaks and talons. but as such I believe is a genetic mutation that hampers the bird's ability to survive. otherwise there may be so many more of these albinos out there than there is.Almost all raptors, if not all hawks have black wingtips. Which I believe is an adaptation to something that does battle on the ground with quarry. But there is another bird that has black feathers, but has extremely flexible feathers, the Harris Hawk. I always thought that melanin stiffened up feathers, not made them flexible. So there's another thought to ponder.
I could cite a reference to the book I read about melanin out of, but I can't find it. I believe it might be Ferguson's first edition Raptors of the World. I learned a ton out of that book.

January 30, 2014 at 11:54 AM  
Blogger Mike Slater said...

Hi Jerry,

I did a little reading about this last spring before I wrote an article about snow geese for my local newspaper column.

There is evidence tha melanized feather barbules are more resistant to wear from abrasion. This is from observation of partial albino birds. Where two feathers could be compared from oppisite side of the birds. The white feathers were more worn.

Another study, reported in the Journal of Experimental Biology in 2004 was of a single Osprey wing feather. The researchers, Michael Butler and Amy S. Johnson, tested the tensile strength of adjacent light and dark sections brom base to tip and found color didn't make much difference. A barbule from a light section and one from an adjacent dark section side had more similar strength than two dark sections that were far apart.

I also think of the other large white birds with black wing tips besides snow geese and many hawks like, Wood storks, White pelicans and white ibis.

I don't know if anyone has correlated this with the frequency that feathers are molted but hat might be revealing.

Mike Slater

January 30, 2014 at 2:02 PM  
Blogger Jerry Liguori said...

H Mike

Yes, an interesting thing is that many buteos don't have as dark on the primary tips as adults do, and the thought is that they only hold the juvenile featrhers for a year but may hold the adult feathers for 2. So, when you see adults that have retained the juvenile outer primaries, those outer primaries are quite worn compared to a bird with adult outer primaries.

January 30, 2014 at 3:14 PM  
Anonymous Hatem Gomaa said...

Hi Jerry.

I personally don't buy it. If that was the case, then why isn't the tail also black or dark tipped?
Why is it something we're trying to associate with raptors only and not the majority of avian species? If hunting on the ground is the sole reason to have strong feather tips, then IMO the tail feathers would be more important than the wings. A bird coming in on a meadow vole or field mouse with it's talons extended and hitting the ground is going to have its tail feathers scraped and scratched and taking a far greater beating from the ground surface than any other body feather. What about other species which aren't necessarily predators or hunters by definition but do catch and eat other animals such as herons or shrikes? They're flight feathers are not necessarily "black tipped" but are just a darker shade of the overall dark body color. The same applies to the Harris hawk and even the Red Tailed hawk. If you look at the dorsal side of the feather, it's just a darker version of the overall dark body color but it only seems more prominent on the ventral side of the feather because most of the underneath parts of the bodies of raptors are lighter colored, so the contrast is much greater and actually deceiving. That's exactly what's happening in Jerry's pictures above. We're seeing the ventral view and that sharp contrast, but if we saw the back of each of those birds, it wouldn't be so prominent and just a darker shade at the tips.

We have a tendency as humans to assign certain characteristics with specific functions and while most of the time we probably get it right, in some others I think we tend to overthink things. I can see the notch in the first five or so primaries being there for a specific function and that's a trait we see in the majority of birds so it becomes much more plausible. But to associate dark (and we're not even necessarily saying "black" because much of that dark is not black but dark brown) wing tips with strength because that specific shade contains more melanin is just not substantial enough. One could probably think of more reasons why it's not than why it is.

January 31, 2014 at 5:46 AM  

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