Re: HIGHER LANDBIRDS & CLAWS

["Tim Williams" <tijawi@hotmail.com>]

Darren Naish wrote:

> Re: manual claws in _Tynskya_. An alular claw is also present in
> _Gracilitarsus_, as the new complete specimen described by Mayr
> (2001) demonstrates.

The paper Darren is referring to is:

Mayr, G. (2001).  A new specimen of the tiny Middle Eocene bird 
_Gracilitarsus mirabilis_ (New family: Gracilitarsidae).  The Condor 103: 
78-84.

There is a very pronounced claw on the alular digit.  _Gracilitarsus_ also 
has a short hallux combined with what Mayr interprets as a facultatively 
zygodactyl foot: "Given that _G. mirabilis_ is correctly assumed to have 
been (facultatively) zygodactyl, it might have been able to perch in trees 
and bushes, whereas the short hallux alone would have limited its grasping 
abilities."  Mayr also cites the size and proportions of the pedal digits 
and claws to argue for vertical clinging in _Gracilitarsus_.

> On the subject of manual claws in neornithines, Alan Gishlick has
> asserted that hoatzin chicks don't use their claws for climbing. I
> disagree with this, having seen footage of climbing hoatzin chicks that
> can definitely be seen to be using their claws.

As have I.  The use of the wing-claws in climbing in juvenile hoatzins is 
also well-attested in the literature.

> Incidentally, I'm especially interested in _Gracilitarsus_ because Mayr
> notes that some of its tarsometatarsal characters recall those seen in
> _Eutreptodactylus_, Baird and Vickers-Rich's 'primitive cuckoo' from
> Patagonia.

On a sad note: according to Mayr, the type specimen of _Eutreptodactylus_ (a 
complete tarsometatarsus) can no longer be located.

> Further to some of Tim's comments on NW vultures: the whole thing
> about vulturids not being part of the Falconiformes s. s. still depends
> on who you ask, or what data you look at. While the molecular boys
> and girls are quite happy to have NW vultures as part of a Ciconiidae
> (Sibley and Ahlquist have storks as Ciconiinae and NW vultures as
> Cathartinae, both within Ciconiidae), some morphological studies (e.g.
> work on syringeal anatomy) support inclusion of vulturids in a
> traditional Falconiformes.

However...there is anatomical/morphological and behavioral support for 
allying NW vultures with the storks.  The NW vulture-stork link was proposed 
no later than 1983 (and probably earlier), before the gene jockeys started 
messing about with DNA (a la Sibley & Ahlquist;Seibold & Heilbig; etc).

(No disprespect is intended toward molecular workers; I'm one myself).

> Finally, while NW vultures generally don't
> kill prey, there are some published observations of turkey vultures
> killing passerines and that sort of thing.

True. Just as predators sometimes resort to scavenging, many scavengers 
include active predation in their trophic repertoire.  But when it comes to 
large prey with tough hides, turkey vultures have to wait in line.


Tim

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