When hunting, Northern Harriers have a distinctive buoyant flight. They glide with wings held in a strong dihedral and have low wing loading which allows them to fly low and slow as they search for prey. When watching them hunt there are times I think they’re going to fall right out of the air.
1/4000, f/6.3, ISO 500, 7D, 500 f/4, 1.4 tc, not baited, set up or called in
Another reason they can fly at such low speeds is their unusually large and prominent alula or “bastard wing”. Just look at the size of it (marked with small red arrow) and then compare it to the alula of a kestrel in flight here.
The function of the alula is similar to that of the slats on the leading edge of the wings of an airplane – it increases the angle of attack of the wing and produces lift, thus helping to prevent a stall during slow flight.
This male harrier at Farmington Bay is flying extremely slowly as it hunts and is so close to the vegetation that its hanging feet sometimes touch it. I suspect that when they use this style of hunting (very slow and close to the ground) they’re attempting to locate prey as much by sound as by sight. After all, the function of their owl-like facial disc (unusual in a diurnal raptor) is to direct sound to their ears.
I sometimes refer to this particular harrier hunting posture as its “hanging posture” because not only does the body hang down from the wings but the bright yellow feet and legs also hang down from the body rather than being tucked up under the rump in a more aerodynamic position.
Ron
Oh My! You have outdone yourself with the shots and information! Thanks sooo much for sharing Ron! You are amazing!
Thanks very much, Charlotte.
Ron appreciate the information about the facial disk. I am so used to seeing it in owls that I overlook it in diurnal raptors.
Your photo makes it very apparent and your explanation explains the hunting low where hearing will be a valuable ancillary skill.
Of course the photo is magnificent. I can almost feel the tension in the bird. Thanks
You’re right about the tension, Diana. This type of flight isn’t easy for extended periods of time because they get very little lift from forward motion – most of it must be supplied by the actual wing beats, which takes a lot of work.
Bill, I’ve tried six links you’ve posted and gotten a page that says the one I’m looking for does not exist. In case you aren’t already aware of this. The ones that have worked have been very informative.
Susan, Bill and I have been working to get his links functional (long story) and there were some duplicate posts with dysfunctional links. I’ve now deleted them.
Thanks, Ron.
Here is the link to the tail structure:
http://i17.photobucket.com/albums/b64/smunster/Diagrams/27092a7f-5bfc-4a34-863e-9c5b4a51fbf0.jpg
Bill
Now that I have figured out my error, here are two links to the wing structure (we talked about the wrist area a while back) and the tail structure of raptors.
Note this is a buteo wing. The structure of the bones is basically the same in all raptors but the feather numbers and shape can vary between species, genus and family.
http://i17.photobucket.com/albums/b64/smunster/Diagrams/5fb2db35-c023-4bf6-9bd6-1937906f9903.jpg
The tail is basically the same in all raptors with the feathers (12) only varying in color and length (sometimes within a species and generally between species). Interesting that feather length varies with most species from juveniles and older feathers of the same bird. Theory suggests the longer wing feathers (primaries) and tail (rectrices)assists the juveniles efforts to fly. After their first moult those feathers will grow in a very small amount shorter. Now making the bird a little more manuverable.
Bill
BTW if you use Photobucket as your photo host and wish to post a link use the direct link. Not the HTML or Image codes. LOL
Hopefully this works. This link will further show the structure of the toes, foot and lower leg of most raptors. Note the feathering finishing at the bottom of the leg. Goldens, Rough-leggeds, Ferruginous and all owls in N.A. are different though. The former 3 species are feathered to their toes and the latter are all feathered to their talons.
http://i17.photobucket.com/albums/b64/smunster/Diagrams/RaptorFoot-1.jpg
Bill
Thank you. Fascinating information (from you and others) and beauty in a single post. Again. No wonder your posts have become an addiction of mine.
That’s one addiction I’m happy for, Elephant’s Child!
Always a thrill to see your gorgeous gray ghost photo. Absolutely love this one with the pose, the light, details, habitat and the bastard wings. Thanks for the very nice explanation. After photographing the barn owls hunting recently, they really remind me of northern harrier (indeed there were one male and one female northern harrier hunting in the same area as the barn owls too) and from their pose sometimes we couldn’t tell which was which until they flew closer. And interestingly, the barn owl didn’t turn their body upside down and dive down everytime. Sometimes they hang lower and lower just like the harriers.
Hi Tin, Nice to see you here. Yes, I agree that Barn Owl hunting techniques can sometimes resemble those of harriers quite strongly (and you’ve sure been posting some nice shots of those owls recently!).
Ron: You made reference to the yellow areas in the Harrier’s “legs” as being “the bright yellow feet and legs”. In reality those areas are the toes and feet. Many people confuse the feet (tarsus) as being the lower legs but the lower legs and upper legs of almost all raptors are covered with feathering. In this case white feathering. The upper leg (thigh) is often hidden by the body plumage. Some raptors are actually feathered on the feet and a few on the toes (owls). I guess I need to finish finding those anatomy (skeletal) diagrams. lol.
Bill
I’m not sure which of these links will work in this format, so I have included two.
[URL=http://s17.photobucket.com/user/smunster/media/Diagrams/5b51b4cc-eb06-45ac-be15-247aa7acc849.jpg.html][IMG]http://i17.photobucket.com/albums/b64/smunster/Diagrams/5b51b4cc-eb06-45ac-be15-247aa7acc849.jpg[/IMG][/URL]
http://i17.photobucket.com/albums/b64/smunster/Diagrams/5b51b4cc-eb06-45ac-be15-247aa7acc849.jpg
Bill
I’m not sure what link to use to post an image here so I am posting these (all for the same diagram). Hopefully one of them works.
http://i17.photobucket.com/albums/b64/smunster/Diagrams/5b51b4cc-eb06-45ac-be15-247aa7acc849.jpg
http://s17.photobucket.com/user/smunster/media/Diagrams/ScanDrawing1001.jpg.html
Bill
How very interesting. No wonder we get confused about birds’ legs. Thank you for posting the links.
That’s something I was aware of Bill but I never know if making that distinction is more helpful or confusing to many folks so I sometimes go along with the flow.
Both of your links work and are helpful in understanding the anatomy. Your comment with the links didn’t show up at first because my software requires my approval for comments with multiple links. Thank you.
Maybe the diagram I posted will help lessen the confusion. People often forget birds stand, perch and roost on their toes (like ballerinas) and sit, set, lay on their feet. Just like was discussed on another photo discussion a birds “parts” of their limbs are much like ours as far a the skeleton goes. The wings and legs especially.
I have some similar diagrams of the foot/toe/talon and wing which I will get into my photobucket account so I can post links with the hopes they will help reduce any confusion.
Bill
This diagram will further help show the toes, foot and lower leg of a species feathered to the foot (but not on the foot of the Golden, Ferruginous, or Rough-legged).
[URL=http://s17.photobucket.com/user/smunster/media/Diagrams/RaptorFoot-1.jpg.html][IMG]http://i17.photobucket.com/albums/b64/smunster/Diagrams/RaptorFoot-1.jpg[/IMG][/URL]
Here is a wing diagram showing the skeletal structure as well as the feathering. (This is a buteo wing but please realize not all buteos have the same feathering.
[URL=http://s17.photobucket.com/user/smunster/media/Diagrams/5fb2db35-c023-4bf6-9bd6-1937906f9903.jpg.html][IMG]http://i17.photobucket.com/albums/b64/smunster/Diagrams/5fb2db35-c023-4bf6-9bd6-1937906f9903.jpg[/IMG][/URL]
Bill
Excellent commentary on alula to enhance excellent photos. I don’t comment often, since your feedback volume is always plenty heavy. But thanks for doing what you do — and for taking us along with you.
I appreciate you saying so, Howard. Thank you.
Very interesting photo(s), Ron. As someone more familiar with airplanes than with birds, I found your explanation of the alula fascinating.
I think the alula is a very interesting structure, Dwynn – from both a functional and an evolutionary point of view.
Wonderful information and beautiful image. He’s magnificent. So is the kestrel and your kestrel images in the linked post. I don’t miss many of your posts, but that was one I missed. Thanks for providing the link back to it.
I’m glad you enjoyed both posts, Sharon. Thanks.
Re. posting your camera settings: thank you so much for doing so. They are extremely helpful. I’m sure I’m not the only visitor to your site who finds the settings an education in and of themselves. Iso 500, 1/4000; a mystical experience.
Thank you, Kelly. I didn’t really need that much shutter speed but light conditions were changing fast and I shoot in aperture priority.
Extraordinarily good flight photographs and commentary. The far wing’s leading edge – three dimensions – beautiful!