Dr Phil Battley, a senior lecturer at Massey University, explains the wing structure and feathers on godwits in terms of flight ability. He describes the flight feathers, how the wing is similar in structure to a person’s arm and hand and how the wing is designed for flight.
Dr Phil Battley
The birds sort of have two sets of feathers, one of which is the body feathers, and they replace those twice a year. So those feathers are used for mate choice and selecting a mate up in Alaska, but they don’t actually contribute to flight. The feathers that contribute to flying are the ones along the back of the wing. They’re called primary feathers are on the hand and secondary feathers are on the arm and their tail feathers.
They replace those when they’re in New Zealand every year. It takes them about 3 to 4 months to grow 10 primary feathers on each wing, so they spend a long time doing it, because these are the feathers that will power their flight and they need those to be as strong as possible. The feathers that they grow here will have to last them for about 30 000 kilometres of flight.
They have the same bone structure as humans do. The piece of the wing you mostly see is the forearm, and the outer part of the wing for a bird is its hand. The trick about a bird’s wing is that the bones are actually only a tiny part of the wing and then these are just used to attach long feathers to. So the bony structure of a bird’s wing might only be the thickness of my finger but it might have 10 centimetres of feathers hanging off it, so feathers can dramatically increase the surface area of the wing, and the wing is what gives propulsion for flight with very little weight.
A feather is a very light structure. It’s hollow down the shaft. The veins off the side consist of these interlocking barbs and barbules – it’s like a little net of keratin fibres. So it’s incredibly light, which means that a bird can get a big surface area to push up with when it’s flying with very little weight to go with it.
The other thing about the way a bird’s put together is that most of the flight muscles for a bird aren’t on the wing at all, they’re on the body. So if we think about humans, we have large muscles on our arms, forearm muscles, biceps. Those muscles on birds are quite small, and it’s their chest muscles that do all the work. Instead, they’ve got just small tendons that run down the wing to pull the wing up or down. It’s another way of keeping the wings light and keeping all the heavy part of the body in the centre where the point of balance is, so a bird’s body is the little powerhouse, and its wings are just sort of held by little pieces of string that flap them up and down – that’s sort of what their tendons are doing.
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