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Re: Bird/hibernation/torpor



John Bois wrote:
> Betty Cunningham also wonders why we have found no such
> associations if they indeed occurred.  Are the following good
> reasons?
> 3. I think mammal bones don't fossilize as well as dinosaur
> nests.

In the Gobi, they've found little shrew-mammals alongside areas with
contemporary dinosaurs.  The conditions for fossilizing seem identical
(they were all covered by a sandstorm).  Dinosaur embryos are probably
harder to find specimens of then mammals and the conditions are even
rarer to have a succesful fossilization, and they've even managed to
find those. AND they're of similar sizes.  Mammals may be rarer simply
because if they were burrowers and were covered by a sandstorm, they
were likely able to escape.  

> By the way, I once read of Andrew's expedition that they pulled
> (Zalambdalestes?) skulls out of dino nest beds (protoceratops?).
> Has anything more been said about that?

good point.  What has happened with these?

> BIRDS:
> You say: "Because most, if not all, dinosaurs, probably buried
> their eggs to at least some degree...raiders of dinosaur nests
> would have to have the ability to dig open the nest.  Such an
> ability is unlikely for most...birds."
> First of all, I think it likely that birds took a terrible toll
> on hatchlings. 

seagulls are probably the major predator of sea turtle hatchlings.
They either find exposed nests and eat at the eggs already uncovered, or
just chase down hatchlings on their way to the sea and gobble them up. 
No special development needed at all to dig eggs.  Weren't gull-or-tern
forms around?
I can see herons doing the same sort of predation with tadpoles.  
There's that recent beach nest site (french?) that could have easily
been sea turtles instead of dinosaurs-sea turtles laying eggs frequently
as far as 100 feet or so from the shoreline.  If sea turtles then were
similar to sea turtles now, the eggs would have been deposited, buried,
and abandoned.  It's likely any hatchling of any species (dinosaur or
turtle) appearing on the beach would have been lunch to ANY predator
there just as it happens today.  
Nowadays we have sea turtle eggs and hatchlings being eaten by man,
dogs, coyotes, rats, birds, snakes, lizards, sea gulls, and just about
anybody else that finds them.
Back then you could probably include other dinosaurs, birds (those
seagull/tern morphs), lizards, rat-like mammals, snakes, and maybe even
pterasaurs.  And that's all before they hit the water!
Sea turtles don't have elaborate built-cover for the eggs beyond sand or
parental protection of their young, and they managed to survive the KT
just fine.

> I'm not sure I could say why
> people are comfortable with the statement: "egg predation
> occurred", and not with: "mammals and birds preyed on dinosaur
> eggs and babies".  Are these statements qualitatively different?

I have no problem with either of those statements.  You should probably
add dinosaurs to the list of egg-predators.
I believe that the discomfort is with the idea where you've said
(something like) "mammalian egg-predation is a major cause of dinosaur
extinction".  Well, maybe on an individual basis, but I don't see all
species of dinosaurs represented at the KT suddenly being hit with a
biblical plague of rats.....seems very untidy in a scientific way.

> My point is that grasses provide cover in areas that were inaccessible to 
> mesozoic
> plants.  

Jack Horner suggested that dinosaurs laid eggs in upland areas similar
to that found around lakes and streams today (because all prior juvenile
remains from the United States were found in near-shore sea deposits). 
Lots of rush-or-rush-like plants like horsetails and ferns and such
around lakes and streams.  He then went and found many such nesting
areas in Montana at Egg Mountain which was just such a site as he
predicted.  With plant material supposedly used as nesting material, so
there was some kind of plant cover on-site.

-- 
           Betty Cunningham  
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