94 MY LIFE AS A NATURALIST 



Why, too, does this perky little bird carry its tail cocked up in 

 the characteristic manner known to almost everyone ? 



The three members of the HirundinidcB, the Swallow (Hirundo 

 rustica), House Martin (Ckelidon urbica), and Sand Martin 

 (Riparia riparia), are interesting from many points of view. 

 Although so closely related, they construct nests of very different 

 types, that of the House Martin being, as a rule, the only exposed 

 nest of the three species. The Sand Martin is, of course, a 

 tunneller, boring a hole about an arm's length in the face of a 

 sand pit, cliff, or river bank, and depositing a nest of grass, 

 feathers, etc., at the extremity. 



Of plaster nest-building birds we have very few examples on 

 the British list, the House Martin being the most famous of 

 these. Why do these three closely allied species differ so con- 

 siderably in nest construction ? An interesting example of an 

 entire plaster nest built by a Nuthatch (Sitta ccesia), at Wad- 

 hurst, Sussex, is recorded in " British Birds," March, 1915 ; 

 the nest, consisting wholly of plaster like a House Martin's, being 

 built in a haystack, and weighing six and a half pounds. It 

 was lined with flakes of bark in a similar way to the more ortho- 

 dox structure. 



I only refer to the Nuthatch here because of this reference to 

 plaster nest-builders, the former, as a rule, hewing out a hole 

 in a tree, and using mud to close up the entrance hole until it is 

 just sufficient to permit the owners to go in and out. An entire 

 plaster nest of this species in a haystack seems worth mentioning 

 by way of comparison. 



The HirundinidoB are infested with parasites. Gilbert White 

 drew attention to this, and I have remembered it ever since 

 reading the delightful letters when quite a boy. White says 

 the birds are infested with Norfolk Howards, which is, I 

 believe, a popular name for a kind of Bug. Is it usual for 

 most birds to be infested with parasites, or do such creatures 

 prey upon Swallows and Martins rather than other birds ? If 

 so, why ? 



The Cuckoo (Cuculus canorus) is a source of perennial interest 

 and mystery, and much might be written concerning many points 

 which have not been satisfactorily cleared up. I will briefly 

 refer to the size of the egg. Here we have a bird about the same 

 size, and very similar in general appearance and upon the wing, 

 as the Sparrow Hawk (Accipiter nisus). Yet the Cuckoo produces 

 as small an egg as that of the common Sparrow, whilst that of 



