120 HIGHWAYS AND BYWAYS. 



bird hatches its first brood in one of the most artistic 

 httle domiciles, substantial and well lined to keep out 

 the cold and wet, but the second and third broods, 

 hatched later in the season when the weather is warm, 

 are put off ^vith a slimsy make-shift of a nest, often so 

 thin and sleezy that one can see the eggs and young 

 throngh the bottom of it as readily as through a sieve. 



The orioles that nest in Pennsylvania do not use half 

 the material that those do which nest in Canada and 

 JSTorthern IsTew York. Old birds in many cases not only 

 make much better nests than the younger ones, but are 

 also much better singers, some of them even adding new 

 bars and strains to their songs. The cow-bunting makes 

 no nest of her own, but deposits an egg in the nest of 

 another bird : this she does surreptitiously and generally 

 as soon as the nest is finished. We all know the inge- 

 nuity exercised by some of the little birds thus imposed 

 on, to prevent the incubation of this foreign egg. 



The blue-eyed warbler {Dendrolca estiva)^ and one or 

 two of the vireos build another department, and wall in 

 the egg of the interloper. So general has become the 

 custom of the bunting to use the nest of the blue-eyed 

 warbler, that the little bird now often makes provision 

 for the emergency when she constructs the nest, by 

 building it deep enough for the two compartments. 



Bird migration has always been an interesting prob- 

 lem to naturalists who do not attribute all phenomenal 

 intelligence to natui'al instinct. It may be called hered- 

 itary instinct, learned through accident, .perhaps, or 

 acquired by necessit}^ and afterwards transmitted from 



