GREAT CRESTED-GREBE 421 



birds under observation daily from dawn till dusk, and I left with the 

 conviction that their coloration must be regarded as "concealing" or 

 " obliterative," at any rate when all the factors of the environment were 

 taken into consideration. For, undoubtedly, in open water there was 

 no difficulty in seeing them even in the distance, but when near a back- 

 ground of reeds they were extremely difficult to detect. But one can- 

 not measure the protective value of this coloration by existing 

 conditions, for these sheets of water are now kept open only by 

 human intervention, by constantly cutting down and rooting up the 

 reeds and floating vegetation. Under natural conditions there would 

 be no large areas of clean water. This admitted, we have next to try 

 and reconstruct the conditions of existence in the remote past, when 

 this livery was evolved. What were the factors of elimination before 

 the advent of man on the scene to disturb the balance of nature ? 

 These we can only dimly realise. But their enemies must have been 

 chiefly raptorial birds, and possibly otters and pike. The silvery 

 breasts probably served as screens from sub-aqueous foes, and the dark 

 brown upper surface performed a like office against harriers, which 

 at that time must have swarmed, and therefore, owing to the keen 

 struggle for existence, have been compelled to depend in part, at any 

 rate, on the grebes for their maintenance. The weak point of this 

 interpretation lies in the fact that the coot, which even to-day lives 

 side by side with the grebe, displays a totally different kind of colora- 

 tion. If it be argued that coots are more numerous than grebes, it 

 must be admitted that the relative values of these liveries cannot have 

 been greatly different, or the grebes would have been exterminated 

 before man came to the rescue, unintentionally, by eliminating the 

 harriers. 



Here then, any way, is a problem awaiting solution, and it may be 

 solved by a closer, more systematic study of the habits of the great 

 crested-grebe to-day. But in attacking this riddle it must not be for- 

 gotten that this bird displays a seasonal change of plumage. That the 

 nuptial dress is the latest acquired there can be no doubt. The 



VOL. iv. 3 H 



