birds navigation, mesozoic birds

[Nick Longrich <longrich@phoenix.Princeton.EDU>]

I think birds can actually use three different mechanisms to navigate-
sun, stars, and the magnetic field. So a failure of one leaves others to
fall back on (so the experiments show- birds can find their way home on a
sunny day with a magnet strapped on, or something like that, but have
problems when its cloudy). I've always wondered how birds dealt with the
flip-flopping of the earth's magnetic poles, but this is probably part of
the explanation.
Also, about shorebirds and terns in the Mesozoic-
AFAIK records of avians in the late Cretaceous are poor. Although Chiappe
claims that Feduccia's model of explosive avian evolution is against good
fossil evidence, I've recently learned a cautionary tale:
    Peter Houde described the paleognathous order Lithornithiformes. In
the process of describing them, he assigned birds, which had previously
been used to establish the earliest records of eight orders of birds, into
this group. They were poorly known fossils that had been placed into
modern bird orders. The end result is a rather modern avian fauna replaced
with an archaic one with far fewer modern representatives. And the good
preservation of early Cenozoic avians suggests that the absence of many
modern orders at this time is because they hadn't evolved yet. Of course,
strictures about negative evidence always apply and the avian fossil
record is a dangerous thing to take at face value.