On Mon, Sep 09, 2002 at 04:13:18PM +1000, Trent Jordan wrote:
> Finally, as an engineer (who's a complete birding novice!) a topic I can
> understand... (sort of...) I'd never really thought about this before, are
> there any good web sites/books out there that talk about birds and their
> flight and energy consumption?
"Bird flight performance: a practical calculation manual" by Colin
Pennycuick (1989 Oxford University Press) is much refered to.
Sadly it doesn't grace my library.
> Andrew's 4 Joules for a lorikeet to fly 4m vertically is fine, but birds
> rarely fly perfectly vertically?... how much energy does it take a
> wedge-tailed eagle to rise a hundred metres or so on a thermal? Come to
> think of it how much energy does one use to take off (obviously more than
> the lorikeet!) You don't have to drive for to long here in NW QLD before you
> come across one that either refuses point blank to hop off the road kill or
> takes an eternity to get off the ground.
A wedge-tail weighs 30-40x as much as Rainbow Lorikeet so in principle
the energy required for it to climb will also be 30-40x. Larger birds do
use disproportionately more energy in flapping flight, the Wedge-tail
might use 50-60x more energy in flapping flight. One significant
difference will be wing-loading. The wedge-tail will have less wing area
per gram, perhaps as much as a factor two less. This combined with its
wing dimensions makes takeoff much more challenging for the wedge-tail.
The reluctant wedge-tail may also be trying to avoid the heat generation
involved too or the water-loss consequent on this.
If a wedge-tail is in a thermal which is supplying sufficient lift, the
work required is small so its energy expenditure on flying maybe small -
maybe only a fraction of its basal metabolic rate.
Andrew
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
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