94 



Protective Coloring in Terjsts. 



A. J. BiGNEY. 



Protective coloring in birds luis been and still is a snbject of great 

 interest to the ornithologist. Since ecological factors are receiving so 

 much attention now on the part of biologists, every item bearing upon 

 variations due to environment is of interest, since it tlirows some light 

 upon the question of evolution. 



One of the most remarkable instances of protective coloring came 

 under my ol)servation during the past summer on the island of Feni- 

 kese, made famous by Louis Agassiz's tirst marine laboratory. This island 

 is occupied by only one family. Nothing is raised except a tew garden 

 plants and sheep. There are otlier inlial>itants of the island, however, that 

 aie more important than sheep— at least to the biologist. These are the 

 terns. Long before one reaches the island he cxin hear the shrill voices 

 of myriads of these birds as they tly about the island almost constantly 

 from daylight to dark. These terns are protected by law and hence 

 have become A'ery numerous. Almost countless thousands are to be found. 

 The sounds of their shrill voices make a lasting impression upon a pe-r- 

 son. The island is entirely made iip of glacial material, here and there 

 C(>ver»Ml with grass. The beaches around the entire island .are (luite wide 

 and covered with granite pebbles of various colors, mostly of a white, 

 gray or slate color, giving them a mottled appearance. The grass and the 

 soil is very much the same in color. The dead grass furnishes a line 

 place for nesting and also for hiding-places for the young birds. In the 

 l)reeding season the nests and young birds are so numerous that one has 

 to pick his Avay carefully, lest he step on some of them. They are so 

 nearly the color of the ground and grass that you can hardly see either 

 bird or nest. If the parent bird is on the nest the deception is almost 

 perfect. 



The most deceptive coloring is in the young birds when they lie out on 

 the pebbles to warm themselves in the sunlight. The imitation is so per- 

 fect that you have to look for some time before you can see the birds. 

 The eggs are mottled in the same way as the sticks, grass and earth that 

 compose the nests. The adult birds are not mottled as are the young 

 birds or the eggs, thus showing that this is truly a protective coloring. 



