Bird Competency

[John Bois <jbois@umd5.umd.edu>]

     I have also invoked birds as agents of egg/juvenile
predation at the K/T.  What is the likelihood that birds were
competent dinosaur predators?

     Correct me if I'm wrong.  Enantiornithines dominated the
late Cretaceous.  Their diversity increased to the K/T.  They
were fully volant fliers.  There is no basis for ruling them out
of either egg-predation or juvenile predation.  Within the
limitations of their physiology we would expect some resemblance
between the niches exploited by modern birds and the niches
exploited in the Cretaceous.  We see convergent evolution, for
example, in the incisor teeth of multituberculates and those of
later rodents.  Are there any _a priori_ reasons for doubting
that many proto-bird species filled similar niches (perhaps not
as well) as those of modern birds.  Could there not have been
raptor-like, owl-like, robin-like, albatross-like
enantiornithines.    
     And then the Neognathae or something very like them (a
"transitional shorebird" from Feduccia) came along just before
the K/T.  Because of poor fossilization and lack of K/T sites, we
may never know whether or not the shore bird species was the
ancestor of all the birds which came after it--as Feduccia
haughtily claims.  Genetic relatedness studies, though, suggest
that all modern birds have a common origin _before_ the K/T.  In
this scenario it is likely that all the enantiornithines were not
killed by a K/T event.  Rather, they were simply outcompeted by
the more agile modern-aspect fliers.

     Now, they were outcompeted not only on the shore but in many
different niches.  Could some of these involve associations with
dinosaurs.  From my point of view the onus is on others to show
why the following behaviors were not probable in either
enantiornithines or modern-aspect birds:
1. A juvenile hatchling dinosaur is snatched up by eagle-like
talons.
2. An open nest is attacked by dropping stones and smashing the
eggs.  We see a similar behavior in gulls as they drop muscles. 
3. A dinosaur nest covered with vegetation is ransacked by
picking up leaves and twigs and flicking them away.  Crows do
this.
4. Stones are picked up in the beak and thrown at the egg
cracking it open.  Before you laugh listen to this in _Bird
Behavior_, by Robert Burton: "A juvenile Egyptian vulture uses a
stone to break open an ostrich egg and then eats the contents. 
Holding a stone in its bill, the vulture raises its head high and
then flings the stone downwards.  Its aim is erratic and several
throws are needed.  Sometimes the sequence starts at a
considerable distance from the egg and repeated throws bring the
stone in range."
     This is amazing!  But aren't we always amazed by the
creativity of nature.  Isn't this the reason many of us were
drawn to a life investigating it?  Then why do you deny that
nature could have been creative in similar ways during the
Cretaceous?  Again, unless there is some _a priori_ reason why
they could not have exploited these resources, THEY PROBABLY DID.
And the more developed the birds became towards the K/T, the more
creative they got!