Naked Science Forum

Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: neilep on 22/08/2007 13:21:16

Title: How do kestrels hover?
Post by: neilep on 22/08/2007 13:21:16

Dear Peeps,

Kestrels, I luff em !...see them all the time hovering away ready to dive in and grab a take-a-way !

But how do Kestrels hover ?....I don't see the Robin that frequents my garden hover !

Does it have an updraft mechanism like a Hovercraft ?....or does it work like those hover mowers ?

I don't know.....but I reckon someone here does.

Title: Re: How do kestrels hover?
Post by: DoctorBeaver on 22/08/2007 13:58:15

They use headwinds so that relative to the air they are flying forwards, not hovering.

Title: Re: How do kestrels hover?
Post by: another_someone on 22/08/2007 16:39:14

Headwinds or thermals - i.e. they are either flying forward into a wind, or they are falling through an upward flowing thermal.

Hummingbirds, on the other hand, do hover in a true sense, but they have extremely fast wingbeats.

Title: Re: How do kestrels hover?
Post by: neilep on 22/08/2007 17:36:07

THANK YOU DOCTORBEAVER & GEORGE,

So, how come I don't see other birds falling into headwinds/thermals ?

You are most kind.

Title: Re: How do kestrels hover?
Post by: another_someone on 22/08/2007 17:57:52

You do, but it depends on the bird.

When a bird is using thermals, or flying into headwinds in the manner of a kestrel, it is basically gliding, and so to do it efficiently, it must be a good glider, which means it needs to have a high aspect ratio wing (i.e. a very long wingspan in relation to its length from front to back).  This is exactly the opposite configuration that would be desired to create high manoeuvrability or rapid take-off (for which you want short wings that can beat fast).

Any bird can fly into wind, and can appear to hover in relation to the ground, but a bird with a high aspect ratio can do so with less wind than a bird with a lower aspect ratio wing.  In gale force conditions, many birds can fly into wind and appear to hover.

Title: Re: How do kestrels hover?
Post by: neilep on 22/08/2007 18:51:47

Quote from: another_someone on 22/08/2007 17:57:52

You do, but it depends on the bird.

When a bird is using thermals, or flying into headwinds in the manner of a kestrel, it is basically gliding, and so to do it efficiently, it must be a good glider, which means it needs to have a high aspect ratio wing (i.e. a very long wingspan in relation to its length from front to back).  This is exactly the opposite configuration that would be desired to create high manoeuvrability or rapid take-off (for which you want short wings that can beat fast).

Any bird can fly into wind, and can appear to hover in relation to the ground, but a bird with a high aspect ratio can do so with less wind than a bird with a lower aspect ratio wing.  In gale force conditions, many birds can fly into wind and appear to hover.

THANK YOU GEORGE,

This is what I was getting at...it must be ' bird dependent' as the Kestrel seems to do it by design !

Notice the tail...I wonder if this is prerequisite for the Kestrel to be able to do what it does so well.

Thanks again

Title: Re: How do kestrels hover?
Post by: Drafl on 08/01/2019 02:50:48

Actually contrary to the other comments Kestrels do actually hover in the same way as hummingbirds do, yes they also use thermals which for some reason seems to be most commonly found in the internet but yeah, they also can hover without