[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Senter 2006, Confuciusornis, and humeral mobility
On Mar 27, 2011, at 8:37 PM, Don Ohmes wrote:
> On 3/27/2011 6:44 PM, Habib, Michael wrote:
>> Except that it isn't actually concrete binary data - how do we know the
>> animal could not fly?
> Heh. Because it is dinner?
Ha; yes, that would be quite the definitive moment, wouldn't it? However, I
don't think the animals were caught or killed in the observation sets you
referred to - unless I am thinking of the wrong field group, didn't they simply
flush the birds and find that the condors usually jettisoned their meal before
launching? Also, there may be a critical aspect of launch *rate* involved - it
is quite plausible that condors with full crops or in still air can takeoff,
but not sufficiently quickly to avoid some of the fleet-footed predators in
their environment. If so, they may refuse to forage on days where emergency
launching will be insufficiently fast to guarantee escape and/or regurgitate
their meals under duress to assure a rapid takeoff (plus it tends to dissuade
predators - nasty stuff). I'm not necessarily saying that one option is more
plausible than the other, only that there are more possibilities than it might
seem at first glance. For example, turkey vultures often empty their crops
when threatened, as well, but they can takeoff at a relatively steep angle from
a standing start - so the vomiting is either simple defense or an extra edge in
terms of weight drop. It is usually considered the former.
> It is hard to imagine a setup that would allow you to say w/ confidence
> "This bird launched in still air on level ground." Mega-bucks...
It actually wouldn't be too terribly difficult if condors were not protected.
As it is, however, capturing condors and flushing them in an enclosed area is
probably not an option. It has been done with other large birds, of course,
and with turkeys they even have force plate data. It's not cheap, but it's not
prohibitively expensive, so long as the animal you want to work on is
available. So yeah, I have to agree - not going to be able to manage a setup
for CA condors anytime soon.
Assistant Professor of Biology
Woodland Road, Pittsburgh PA 15232
Buhl Hall, Room 226A