288 Wonders of the Bird World 



apparently lying on the ground." l The fact of the young 

 birds possessing this instinct of self-preservation, vouched 

 for by such an observer as Alfred Brehm, is a most 

 interesting one, and Mr. J. G. Keulemans, the great natural 

 history artist, assures me that he has witnessed the same 

 thing himself. On one occasion he saw a party of Hoopoes 

 routing about the roots of an old tree in a gravel-pit, and 

 on their being startled, every bird seemed to disappear as 

 if by magic, although not one of them flew away. They 

 had simply made themselves invisible on the gravel in the 

 way mentioned above, and this manoeuvre must be greatly 

 aided in sandy localities by the sandy colour of the bird's 

 body. The way in which animals of the desert resemble 

 their surroundings is well known, and a most instructive 

 case representing this phenomenon is to be seen in the 

 Great Hall of the Natural History Museum. There is 

 exhibited a square yard of actual desert from Cairo, with 

 the animals which frequent it, and the student can see 

 that not only the birds, but the small Jerboas and Mice, as 

 well as the Lizards and Snakes, are all of a desert-colour. 

 It stands to reason that, if they were not thus light-coloured, 

 they would be detected by their enemies with great ease, 

 and hence the advantage of protective colouration. 



Another instance of this phenomenon in a northern form 

 of bird-life is afforded by the Ptarmigan (Lagopus mutus) 

 and the Willow Grouse (L. lagopus), which undergo three 

 changes of plumage in the course of the year, and these 

 changes are performed by male and female alike. They 

 are, moreover, necessary for the preservation of the species 

 in the countries inhabited by the birds, for were the 

 Ptarmigan or the " Ryper " to maintain their dark plumage 

 through the winter when snow covers everything, they 

 would at once be detected, and the same would be the case 

 if they remained white throughout the summer, when the 

 1 ' Bird Life,' p. 623. 



