Peter Pfeiffer's note on Kookaburras hopping after prey on the ground is an
interesting one. I found the following extract in Jean Dorst's 'The Life of
Birds' Vol.1 (Weidenfeld & Nicholson, 1974).
"Ground-travelling birds move in two different ways, each accompanied by
anatomical modifications to the hind limb which can be detected even within
the passerines. Those which are adapted especially to life on the ground
walk and run, moving their legs alternately. Their bodies are usually long
and carried horizontally, their toes long but with short claws, except for
the first toe which carries a long and almost straight claw.
"This mode of progression has the advantage that it involves only small
oscillations of the centre of gravity, and so is very economical of energy.
It is therefore the gait of the truly terrestrial birds, which run from
danger instead of flying and never willingly perch on trees. It is seen
also in some small passerines such as larks, pipits and the Snow Bunting, in
larger ones such as the Starling and the Crows and of course in other
terrestrial groups such as the game-birds...
"Other birds, all of them small passerines, move over the ground by a very
characteristic hopping, the series of jumps being interrupted by pauses.
This gait is only possible to small birds, since for larger ones it would
involve disproportionate expenditure of energy. They can move fast on the
ground for a short time, while most of their life is spent in trees to and
from which they take flight at the least alarm."
However, Kookaburras are not small passerines. Peter's comment that they
look 'pretty stupid' translates to looking 'pretty clumsy' because they are
not well adapted anatomically to hopping, but their opportunistic
flexibility in chasing food also means something close to 'pretty clever'.
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