INTRODUCTION. 19 
to be less than 84 inches we are justified in calling the duck a teal (F or FF). 
The light blue shoulders are quite distinctive and our specimen may be 
labeled Blue-winged Teal, provisionally. It remains to turn to the full 
description of this species on a following page, confirm our diagnosis, and 
try to decide whether this individual is male or female, adult or immature. 
As a second example of the use of the artificial key let us take the common 
Blue Jay. Starting with the Key to the Larger Groups, we find that our 
specimen agrees successively with the following lines: 
AA. Not at all web-footed. 
GG. Tibia feathered down to heel joint (“knee”). 
QQ. Upper mandible without cere or soft membrane at base. 
TT. Three toes in front. 
VV. Nail of middle toe not pectinate. 
WW. Tail feathers not spine-tipped. 
XX. Birds more than four inches long. 
YY. Hind toe and claw more than half as 
long as middle toe and claw.— 
Passeres. © 
This shows that our specimen belongs in the order Passeres or Perching 
Birds, and we turn to the key to the members of that group. Here we find 
a Key to Families, and following the same plan as with the previous key 
we decide that our bird agrees successively with the lines: 
2. Upper mandible imperfectly or not at all hooked, toothed, or notched 
at tip. 
CC. Tips of folded wings not reaching to tips of middle tail feathers. 
EE. Tail not tipped with bright yellow. 
FF. First primary about one-half the length of the longest. 
N. Tail feathers with soft, rounded tips. 
OO. Wing 5 inches or more. Family Corvidae. 
Under this heading, we find a Key to Species which gives us in regular 
order: 
AA. Smaller birds, wing less than 10 inches, plumage not all black. 
CC. Tail moderate (about 6 inches), somewhat rounded at tip. (This 
refers not to the tips of the individual tail feathers, but to the 
outline of the whole end of tail.) 
D. Head with a conspicuous crest; plumage largely blue—Blue Jay. 
Turning now to the full description of this species, and noting the 
measurements of total length, wing, tail and bill, it is easy to confirm 
the identification. Incidentally it may be noted that in spite of the 
fact that the Blue Jay is conspicuously blue, the question of color is en- 
countered but twice in the passage through the keys, once in the key to the 
families (“tail not tipped with yellow”), and again at the end of the key 
to species, where “plumage largely blue” is the final characteristic which 
marks the Blue Jay, although even here it is a secondary consideration since 
the “conspicuous crest” is of first importance. Of course it would be possible 
to make an artificial key using color as the most important feature, which 
would lead us more directly to the“Blue Jay, but it would be a very difficult 
matter to make such a key equally good for the many other species which 
