My last message today -- please don't time me out... :-]
Josef H. Reichholf has addressed this in one of his papers on this subject, and at least he wrote that modern physiology has the possibility to quantify things like that. I don't know whether he or anyone else has done this in the meantime.
Anyway, I haven't clearly stated in my paper that birds with protein-poor diets such as parrots moult rather rarely and irregularly, while birds with protein-rich diets like clam-eating ducks moult rather often and shed lots of feathers at the same time. Often female birds invest some of their excess protein into the eggs which are large for vertebrate standards, while the males at the same time develop a display plumage that is later shed.
Right. Archaeopteryx lived in the sea, but it is neither the ancestor nor the sister group of birds under my phylogeny...
I've heard recently that dippers don't fly much when underwater, but rather walk on the ground perching on pebbles because their density is so low. This is not to be expected in more basal coelurosaurs, though, at least not in this extent, and after all, dippers do fly underwater. They obviously have evolved this lifestyle after the ability to fly; we only have negative evidence about whether the opposite is possible.
A very big book (its original edition is English, but the original properties of it are not cited) about living vertebrates of the world mentions: "The 5 species of this family [Cinclidae, monotypic] are at home in Europe, Asia, North and South America, usually in highlands at fast-flowing mountain rivers. [No indication as what "not usually" is.] Among songbirds dippers are the only true water-living ones; in spite of this they don't have webbed feet [like Archie...] and as the only unambiguous adaptation to their watery milieu they have mobile flaps of skin over the nostrils which prevent water from getting in. Dippers can well dive and swim under water. They even can run over the river floor. The males are slightly bigger than the females." Then the Grey Dipper, Cinclus mexicanus, is described and figured. "Habitat: Mountain rivers; Length: 18--22 cm". There is a European Dipper, C. cinclus. That's all the information I have.
Yes... I fear there's only negative evidence for this, too.
This is the way exaptations work: an adaptation allows the animal to do something the adaptation wasn't designed for, and this use offers an advantage, even though that use is not necessary for survival, it is just an advantage (which leads to more food --> more offspring --> an advantage in natural selection). I think (see the Ebel paper) that this sort of underwater flight can lead to air flight quite fast.
My personal feeling is based on the evidence I gave -- what is your evidence?
Ebel mentions a strong argument against ground-up -- chickens can fly but don't like to do so when unnecessary (I've posted this a few days ago) -- after he has debunked trees-down, of course.
I dunno, maybe rex just hunts at night, so Horner and company don't see them. :)
Larry Smith in http://www.cmnh.org/fun/dinosaur-archive/1994Mar/0046.html