*5° 



SPRING 



half-domesticated life. A single martin's nest is the exception 

 on any house, and when there is only one, this isolation can 

 generally be traced to persecution by sparrows, or to spring 

 storms which decreased the bird's numbers. But one pair of 

 swallows will often settle in some lonely byre ; and they 

 seldom or never build a cluster of two or more nests, as the 

 martins do. The differences of the nesting-sites are reflected, 

 as is generally the case, in the colour of the eggs. Swifts, 

 house-martins, and sand-martins lay pure white eggs, like 



SAND-MARTINS 



most birds which incubate in a deep and sheltered hole. The 

 artificial cavity of the house-martin's nest gives the same 

 protection as the holes burrowed by the sand-martin, and the 

 crevices frequented by the swift. But the eggs of the swallow 

 are well spotted with dusky red, and thus conform to the general 

 scale of density in marking which characterises eggs laid in 

 open nests, but not so excessively exposed as to need a 

 highly protective pattern. The insecurity of the swallow's 

 eggs as compared with those of its relations is shown in 

 another way. It would be quite impossible for a cuckoo to 



