56 THE STORY OF THE BIRDS. 
When it is to the interest of the bird to be incon- 
spicuous while perching, these marks may be entirely 
concealed, as in the white rump patch of the flicker, 
which is usually hidden by the closed wings; or in 
the white outer tail feathers of the snowbirds and 
others, which, except when spread in flight, are hid- 
den under the others. 
Other birds are white beneath and protectively 
colored above. The “teetering” of the little “ tip- 
up” sandpipers is doubtless the vestige of a signal 
wrought in the display of white underwear with the 
“peek-a-boo” up-and-down motion. From above 
their colors harmonize with their haunt. 
These “recognition colors” may be also modified 
or used for ornament, since many of them are more 
conspicuous in males than females, as in Bobwhite, 
the English sparrow, and others. In fact, Mr. Wallace, 
who first emphasized these markings as thus useful, 
thought that the purpose of all brilliancy and pe- 
culiar patterns in the males might be simply recog- 
nition markings, whereby the feathered maiden might 
know her beau when she saw him; but it is more 
probable that primarily brilliant colors were usually 
intended for ornament only or the expression of vigor. 
White, however, is often used as ornament also. 
While not literally within the scope of our topic, 
there are among the birds other social signs and ex- 
pressed solicitations for each other’s welfare, which 
might as well be mentioned here because they are of 
a similar nature and origin. 
The well-known assemblage of crows, jays, and 
