CONCEALED OR COVERED NESTS 131 



adopted for concealment, common to more or less 

 extensive families or even orders of birds, it is not 

 difficult to suggest a general reason for them ; but 

 in other groups, where these special means are less 

 frequent or even exceptional, we are often at a loss 

 to suggest any probable explanation. Diverse, how- 

 ever, as are the methods of concealment adopted by 

 the species described in the present chapter, the same 

 great end is gained. 0« the one hand we must take 

 into consideration the fact that a very large propor- 

 tion of the birds that rear their young in these con- 

 cealed or covered nesting places are very conspicuous 

 in colour, and also that their eggs are white, or at 

 least very pale in general coloration. Both showy 

 parent and conspicuous egg require concealment, and 

 this is obtained in that variety of ways the present 

 chapter has sought to describe. For instance, the 

 Kingfishers, the Jacamars, and Bee-eaters are excep- 

 tionally gaudy birds, and all lay white eggs ; hence 

 we may very naturally attribute their burrowing 

 habits to a necessity for concealment during the 

 comparatively helpless period of incubation. Then 

 we have the equally showy Woodpeckers, Hornbills, 

 Toucans, Trogons, Parrots, Rollers, and so on, which 

 seek a similar immunity from danger in holes of 

 timber. Then, again, we have various other groups 

 of species that nest in concealed or covered situations 

 from other motives. The Petrels, for instance, are a 

 group in which crepuscular or nocturnal habits almost 



