[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Science feather strength debate



Erik Boehm <erikboehm07@yahoo.com> wrote:


> Of course the first birds would be weak fliers relative to most modern birds.
> In theory, a modern loon could soar thermals, and in certain environments 
> routinely go hundreds of miles without flapping....


I'm getting a sense of deja vu...

http://dml.cmnh.org/2008Sep/msg00486.html

"But they [loons ] do fly over land between water sources, are occur
over coastal ocean environments that produce marine thermals. Lack of
access is probably not the constraint. Of greater importance is their
aerobic capacity and flight speed - loons are highly adapted for
rapid, straight flight over long distances. They can sustain constant
flapping for very long periods, cruising at speeds comparable to some
freeways. Given their very wide circle radius, and high min sink
(relative to other birds), loons are looking at rather poor cross-
country travel rates using thermal soaring as compared to continuous
flapping. Note that many other birds with similar planforms and muscle
compositions also rarely (if ever) utilize thermal climbing, including
many that travel overland and certainly come in contact with thermals.
Such taxa don't completely avoid external sources of lift, of course -
cloud streets and ridge lifts may be used, for example, but thermal
circling is rarely utilized by animals like ducks, geese, loons, or
grebes."