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Re: CASSOWARY DIMORPHISM



>In fact, one is hard pressed to find any mention of the 
>hyperenlarged sickle-claw of cassowaries in the literature 
>(though there are frequent mentions of the horrific disemboweling 
>kicks the birds can wield), and to my knowledge no-one has ever 
>observed sexual dimorphism in the claw. Want to co-write a paper 
>Jim?;)
>
>"They don't see it. None of them see it. But I see it"
>
>DARREN NAISH

The Handbook of the Birds of the World (Vol. 1) does not mention claw
dimorphism, but notes that "females tend to be larger and more brightly
coloured, and have larger casques than males".

Before we get too carried away with comparisons between cassowaries and
Oviraptor, though, let's take note of an earlier paragraph in the same
account:

"It used to be thought that [the casque] was formed by a bony extension of
the skull, covered by a horny growth.  However, recent research on the
Southern Cassowary has shown that there is no prolongation of the skull,
and that the centre of the casque consists of a very tough, elastic,
foam-like substance.

"The function of the casque has been debated at great length, but remains a
very poorly-known subject.  The standard version is that the birds use the
casque in the forest,both to force their way through dense vegetation, and
also to avoid head injuries in the process.  However, these possible
functions do not appear sufficient on their own to justify development of
this curious structure, for the casque grows slowly throughout the bird's
life and can only provide efficient protection in adults.  Observations of
captive birds using the casque as a shovel indicate a second possible
function, that of searching for food hidden in leaf litter on the forest
floor.  In addition, the casque, like the wattle, is probably an indicator
of dominance and age among individuals of the same species, and it may play
an important role in social behaviour."
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net