The Making of Species 



the herd, it will not be to their advantage to 

 follow the line it has taken. Moreover, being at 

 the rear of the flock, it is not in a good position 

 to take the lead, and its pursuer is likely to see 

 the danger signal before its friends do. It would 

 thus seem that " danger signals," while possibly 

 sometimes of service to their possessors, are on 

 the whole ornaments which might profitably be 

 dispensed with. Natural selection can scarcely 

 be charged with the production of a character of 

 such doubtful utility to the organism. 



Moreover, flourishing species of many 

 gregarious animals do not possess any " signal 

 flag of danger," while, on the other hand, a great 

 many solitary species display markings that 

 render them very conspicuous when in motion. 

 Take the case of the famous Indian Paddy Bird 

 (Ardeola grayii). This, when at rest, is coloured 

 so as to be very difficult to distinguish from its 

 surroundings, but flight transforms it, for it then 

 displays its milk-white pinions, which would 

 make a perfect danger signal, if only it were not 

 peculiarly solitary in its habits. Its gregarious 

 brethren, the Cattle Egrets (Bubulcus coromandus), 

 on the other hand, display no danger signal. 



That these recognition marks prevent the 

 intercrossing of allied species and the production 

 of infertile hybrids appears to be pure fiction. 

 As we have already shown, hybrids between 

 allied species are by no means always infertile. 



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