4 INTRODUCTION 
more, then twist into a confused ball, then shoot out straight 
again, then stop, with a pair of the footprints opposite each 
other, different from the other end of the track, that began 
as two or three little indistinct pits or scratches, not forming 
perfect impressions of a foot. Where the track twisted there 
are several little round holes in the sand. The whole track 
commenced and finished upon the open sand. The creature 
that made it could not, then, have come out of either the 
sand or the water; it must have come down from the air—a 
two-legged flying thing, a bird. To determine this, and, next, 
what kind of bird it was, every one of the trivial points of the 
description just given must be taken into account. It is a 
bit of autobiography, the story of an invitation to dine, ac- 
ceptance, a repast, an alarm at the table, a hasty retreat. A 
bird came on wing, lowering till the tips of its toes just 
touched the sand, gliding half on wing, half afoot, until the 
impetus of flight was exhausted; then folding its wings, but 
not pausing, for already a quick eye spied something inviting ; 
a hasty pecking and probing to this side and that, where we 
found the lines entangled; a short run after more food; then 
a suspicious object attracted its attention; it stood stock-still 
(just where the marks were in a pair), till, thoroughly 
alarmed, it sprang on wing and was off. 
Following the key further, he draws more conclusions. The 
tracks are not in pairs, so the bird does not belong to the perch- 
ers; therefore it must be a wader ora swimmer. There are no 
web-marks to indicate the latter; hence it is a three-toed walk- 
ing or wading bird. It had flat, long, narrow, and pointed wings 
because it came gliding swiftly and low, and scraped the sand 
before its wings were closed. This isshown by the few scratches -: -- 
before the prints became perfect. A certain class of birds thus 
arrests the impetus of flight. It had a long feeling-bill, as shown 
by the little holes in the sands where the marks became entan- 
gled; and so on. These combined characteristics belong to one 
class of birds and to no other; so he knows as definitely as 
1 Elliott Coues. 
