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Re: Feeding of Archaeopteyx



>Someone compared Achai feeding to the methods used by egrets
>and herons and suggested that the forelim bs were used as canopies.
>I can't really imagine an egret o r a heron holding out its wings
>wh ile feeding.  They just don't do th at.
>
>DAvid

I'm sorry, but they certainly do, or some do.  It is an extremely
well-known, well-studied behaviour. From "The Herons Handbook" by Hancock
and Kushlan (1984):

"Use of the wings while feeding is fairly common.  In some behaviours wings
are used by standing or walking birds.  While Wing Flicking, a heron quickly
partially extends and then retracts one or both wings.  While Open Wing
Feeding, a heron extends one wing and leaves it extended for a few seconds
before retrascting it.  While Underwing Feeding, a heron puts its head under
an open wing in order to strike at a prey item.  While Double Wing Feeding,
a heron brings both wings forward and holds them over its head.  While
Canopy Feeding, a heron brings both wings forward above its head so that the
forward edges meet and feather tips dip in the water; this forms an umbrella
over the heron's head and neck.
"These wing movement behaviours may function in different ways.  Wing
Flicking and Open Wing behaviours are probably used to disturb prey, whose
consequent movements increase the heron's chance of seeing them.  Underwing,
Double Wing and Canopy Feeding reduce glare, making prey more visible, and
may attract prey to the shade formed by the wings.  Canopy Feeding is often
assumed by a heron with its back to the sun.  Although many herons use these
behaviours, some do so characteristically.  Open Wing Feeding is typical of
the Reddish Egret.... Pied Herons, Tricolored Herons, Snowy Egrets and reef
herons also use it.  Underwing feeding is also used by Tricolored Herons and
by Reddish and Snowy Egrets.  Double Wing Feeding is used especially by
Reddish Egrets, but, so far as is known, only Black Herons use Canopy
Feeding.  This latter species walks or runs from place to place, stopping
every few steps to form a canopy over its head."

 I have seen this myself in the two species best known for using it, the
Reddish Egret of the southern US and Caribbean and the Black Heron (or
Egret) of Africa, whose Canopy Feeding performance is one of the most
startling behaviours to watch of any bird I know.

However, I must confess I am not much attracted by the suggestion that
Archaeopteryx fed in this way (though, of course, who knows?).  These
behaviours in herons are associated with highly derived modifications of the
head (including placement of the eyes), beak and neck, permitting the bird
to accurately sight on and quickly sieze or impale underwater prey from
above the surface (not to mention long legs for wading) - and the advantage
of such behaviours would seem to be minimal unless they can be followed with
a swift, accurate strike.  Birds that feed on more sedentary water creatures
tend, instead, to find them by touch (eg spoonbills, some storks) and do not
share the sort of behaviours seen in herons.

Archaeopteryx, on the other hand, seems to lack any such special adaptations
(subject to a palaeontologist telling me otherwise).  Although I don't like
to speculate, my own imagined view of Archie is as a generalist feeder, sort
of a cross between a chachalaca and a crow or  jay.  I can certainly imagine
it scavenging or foraging along the shoreline, running down small lizards,
mammals or insects, perhaps robbing nests of smaller dinosaurs, clambering
around in bushes or low trees - but my imagination stops short at its
adopting a heron's lifestyle without any of the special adaptations that
make such a lifestyle possible.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
Home: 1825 Shady Creek Court                  Messages: (416) 368-4661
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net
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Toronto, Ontario Canada M5H 3P5