Geoscience Reference
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oz)—would be very difficult to track. But nearly all other flighted birds, from
wrens to condors, come to earth and make abundant and easily identifiable tracks.
Of course, some flightless birds—such as rheas, emus, ostriches, and cassowar-
ies—make the largest amount of tracks, and the largest tracks period. But many
flighted birds regularly come in contact with the ground as part of their everyday
lives and are thus capable of leaving tracks, too.
Bird tracks can be divided into four main categories based on overall form, all
of which are derived variations of theropod dinosaur feet: anisodactyl, palmate, to-
tipalmate, and zygodactyl. Anisodactyl is the easiest of these to link to Mesozoic
dinosaurs, as it consists of three forward-pointing toes and sometimes a more back-
wardly pointing one (digit I). In some birds, though, this toe also may be reduced
in size or absent. All songbirds have anisodactyl feet, as do chickens, turkeys, vul-
tures, and raptors, as well as most wading birds and shorebirds, such as herons and
plovers respectively. Palmate is a condition in which a basic anisodactyl foot has
webbing between its main three digits, like on the feet of ducks, geese, and gulls.
Totipalmate feet take this form a little further with webbing between all four toes,
making for impressively broad tracks, such as those left by pelicans. Zygodactyl
feet have their digits arranged with two pairs of toes and each bunched together to
formeitheraKorXpattern.Thesefeetaretypicalofowls,roadrunners,andwood-
peckers.
Eachbird-footformreflectsadaptationsselectedoverthousandsofgenerations
ofbirds,meaningthateachtrackmadebyabirdalsoreflectsitsevolutionaryhistory
and adaptations. For example, the extremely long, widely spaced, and thin toes of
some wading birds, such as moorhens, are well suited for walking on lily pads in
freshwater ponds. The three forward-pointing and single backward-pointing toes of
songbirds are excellent for grasping and perching on branches. The webbed feet of
ducks, geese, and pelicans aid in their surface swimming and diving in either fresh-
water or marine environments. Woodpecker feet work quite nicely for moving rap-
idlyupanddownverticaltreetrunks.Raptorandowlfeetareverygoodatgrabbing
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