444 A HISTORY OF BIRDS 



exclusively— frogs, fish, water-voles, and so on ; but the Crane, on 

 the other hand, seems to prefer a vegetable diet ; and to procure 

 this large flocks will betake themselves to corn-fields wherever 

 these are to be found. These birds are not, however, entirely 

 vegetivorous, for frogs and lizards are greedily devoured ; fish, 

 however, they do not appear to eat. 



Another striking instance of convergent evolution is furnished 

 by a small and very remarkable family of the Plover tribe — the 

 Parridae. Extending over a wide geographical area, inasmuch 

 as representatives are to be met with in Australia, South 

 America, India, China, Ceylon and Africa, they yet all present 

 a very un-plover-like appearance, and a strong resemblance to 

 the RalHdae, a family allied to the Cranes. 



The Plovers, we may remark, are small, medium-sized, 

 short-toed wading birds, frequenting beaches, and marsh and 

 fen land, but keeping strictly to open country. Many swim 

 with ease, though they appear but rarely to resort to this 

 exercise. 



The Rails and Water-hens are birds which should need no 

 description here. Dwellers in the country know them well, and 

 even in great cities like London the Water-hens at least may 

 be seen daily in all the larger public parks, where indeed they 

 have shaken off the reserve and secretiveness which are their 

 natural habit, and walk boldly in the open. Timid and retiring 

 in a wild state, these birds are not easily approached. In their 

 haunts they differ from the marsh-loving Plovers in that they 

 hide amid the densest cover the reeds afford. When they come 

 abroad they prefer to take to the water. Contrasting strongly 

 with the Plovers in the great length and slenderness of the toes, 

 these birds yet swim and dive well, though, be it noted, the 

 toes are not webbed. This elongation of the toes renders it 

 possible to walk with ease over floating water-weeds where 

 insect prey abounds.^ 



Thus, then, the Plovers and Rails contrive to live in har- 

 mony in the same regions. This brings us to our objective the 

 evolution of the Parridae. There are several species in this 



^ It might be supposed, perhaps, from this description that the Plovers and 

 Rails were all aquatic or semi-aquatic in habit. This is not the case ; a few 

 species in each group have become dwellers on dry uplands, like the Land- 

 rail ; or sandy wastes, like the Thick-knee (p, 54). 



