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gists to recognize scratch marks on fossil tree trunks and branches, and to distin-
guish scratch marks made by climbing versus running while flapping. Although not
completely impossible, such evidence would have a much lower preservation po-
tential than those made on muddy or sandy surfaces. The best trace fossils related
to this hypothesis, of course, would be those showing the landing marks of an awk-
ward baby dino-bird—complete with feather impressions—that also show it walk-
ing away from its crash site, successfully surviving a fall from a nearby tree.
Have non-avian dinosaur tracks indicating flight, however brief, been recog-
nized from the fossil record? Not yet. However, some Early Cretaceous (about
120-million-year-old)small-shorebirdtracksfromKorea,reportedbyAmandaFalk
and others in 2009, bear some of the same traits I just described for landing and
take-off tracks. In 2013, Pat Vickers-Rich, Tom Rich, and I interpreted two of three
closely associated anisodactyl tracks from Early Cretaceous rocks of Victoria, Aus-
tralia as bird tracks, with the third coming from a non-avian theropod. These turned
out to be the oldest bird tracks known in Australia, dating from about 105 million
yearsago.Oneofthetracks,madebyabird'srightfoot,alsohadanelongatedmark
left by digit I, matching modern examples I've seen formed by herons in their land-
ing tracks. Unfortunately, the slab of rock was broken along the front edge of this
track, so we could not further test our provocative hypothesis by checking whether
another track was paired with it, and bearing the same marks of flight. When we
published our results, we encouraged other paleontologists to start thinking about
evidence for flight whenever studying Cretaceous tracks, whether these were from
birds or non-bird theropods.
One last point I would like to make about bird tracks, and a surprising one to
many people, is how these traces can actually alter environments. For instance, if
youeverseemudcracksinanareafrequentedbybirds,takeacloserlookatthegeo-
metry of those cracks and you may see the familiar three- or four-toed patterns of
bird tracks in them. I first noticed this phenomenon during a hot summer in 2004
while walking along the edge of a pond on San Salvador Island, Bahamas. Yellow-
