368 ENGLISH BIRD LIFE 



the Puffin's, but they are all undoubtedl}^ white. 

 Indeed, I can call to mind few purely white eggs 

 laid in the open. The Wood-pigeon's might be 

 instanced, but the dense coverts which the bird 

 affects almost equal in gloom the cavern which 

 the common ancestors of the tribe first chose 

 for a nesting-place. With the Swallows, three, 

 including the Swift, which nest in almost total 

 darkness, lay white eggs, and one, whose nest 

 is comparatively open to the light, has eggs pro- 

 fusely spotted with ash-grey and brown. These 

 facts may have some bearing on the question of 

 protective coloration. Or it may be that they are 

 merely a little trick of Nature's, which she does 

 not condescend to disclose, as, for example, why she 

 makes the tip of a black and wdiite cat's tail invari- 

 ably black, and the tip of the tail of a black and 

 white dog invariablv white. 



Here by the river the first Swallows usually 

 appear. On one bright April morning, a drowsy 

 bird fiorure, usuallv a Sand Martin, is seen flit- 

 ting across the water, the herald of the returning 

 migrants. Only for an hour or two, when the 

 sun is warm, may it be seen; as the day darkens 

 it will be looked for in vain. It is easy to under- 

 stand how the once commonly accepted belief in the 

 hibernation of Swallows came to be held. The 

 sleepy appearance of the first comers, their apparent 

 w^ithdrawal when the sun ceases to shine, their 

 habit of assembling close to the river when the time 

 for migration draws near, these facts gave a certain 

 colour even to the bold assertion that Hirundo 

 evaded the winter W'inds by the simple expedient 



