396 THOMPSON, Directive Coloration of Birds. Ae 
The general rule may be topographically rendered: Color of 
upper parts, Protective ; color of lower parts, Directive. In the 
drawings, I have shown only certain birds of prey. All of these 
present a distinctive pattern when viewed from below as they fly. 
It is inconceivable that this pattern should have a protective 
object, so if it have a purpose at all it must be a directive one. 
An evidence of this is seen in the fact that all birds with 
ample wings and habits of displaying them bear on them dis- 
tinctive markings—e. g., Hawks, Owls, Plovers, Gulls, ete. 
Every field man will recall the pretty way in which most of the 
Plovers identify themselves. As soon as they alight, they stand 
for a moment with both wings raised straight up to display the 
beautiful axillar pattern; a pattern distinctively different in each 
kind. And no doubt their end is served by telling friend or foe 
alike that this is such and such a species. 
On the other hand birds whose wings in flight move too 
rapidly for observation are without markings on the underside. 
Referring to the plate (Plate IV), several interesting conclu- 
sions may be drawn. 
Though it is proverbially dangerous to classify animals with a 
view to one set of characters only, it is nevertheless interesting 
and often instructive. Among the Hawks the presence of the 
wrist spot characterizes the Axwfeo group including the Eagles 
and the Osprey. 
The Falcons on the other hand, in common with the Accipitres 
and Circus, are without the wrist spots and have nebular banded 
primaries. 
Exceptions to the rule that directive marks belong to the lower 
surface are seen in the Redtail, whose rufous tail is its most 
distinctive mark ; in the white rump-spot of the Marsh Hawk and 
the head-markings of Goshawk, Peregrines and Sparrow Hawks. 
Among the Owls the wrist spot seems to characterize those 
that have ‘ ear tufts.’ 
In this brief paper and single plate I have limited myself to 
our northern birds of prey, but enough material has been 
gathered to justify a much more extended application of the 
generalizations indicated. 
