RE: Life of Birds (vertical running)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dinogeorge@aol.com
> Sent: Wednesday, October 10, 2001 12:43 AM
> To: dinosaur@usc.edu
> Subject: Re: Life of Birds (vertical running)
>
>
> In a message dated 10/9/01 8:49:32 PM EST,
> ofsosa@uclink4.berkeley.edu writes:
>
> << They aren't grasping the trunk, they are actually running up
> it, using the
> force of their flapping to hold them onto the tree. Arboreality is not
> required. >>
>
> What do you mean, "Arboreality is not required"? This running-up-a-tree
> business is arboreality >by definition<. Why would they run up a
> tree if they
> were just going to come right back down again to >avoid< being arboreal??

And yet (and I don't want to say too much about it, so that Dial's paper
isn't comprimised) the taxa that were studied that demonstrated this
behavior are all NON-arboreal birds!!  They are the groups colloquially
called "ground birds" (chukkar's being the main star of the presentation).
Ground birds all tend to feed on the ground, but boy do they ever want to
get up into trees, roofs, rafters, etc. when not feeding!  (I've seen
peacocks getting way up into trees: maybe 10 m or more high, and yet no one
considers peacocks "arboreal").

Neither the foot and leg adaptations nor the forelimb motion used in this
"wing assisted incline running" or whatever they are going to call it are
things which are absent in maniraptorans basally.  Extremely, extremely
cool.

I am going to state publically that I now agree that Greg Paul et al. are
almost certainly correct in the following aspect: the broad feathers and the
forelimb adapations of dromaeosaurids, troodontids, and oviraptorosaurs are
almost certainly associated with an avian style form of locomotion.
However, to qualify that: that locomotion is almost certainly NOT flight,
and I don't think there is any secondary loss involved: I strongly suspect
that young members and small adult individuals of these taxa practiced this
locomotion.

If anything, Dial's presentation shows us to drop our old definitions NOW.
They have only crippled our understanding of the origin of flight.  "Ground
up", "trees down", "arboreal hypothesis", and "cursorial hypothesis" are
intellectual baggage that should be left behind.  Instead, let's go out and
watch some birds.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796