MOORHENS AND COW-BIRDS 273 



do. Certain of the cow-birds of America have, 

 it seems, the habit of pecking holes both in their 

 own eggs and those of the bird in whose nest they 

 are laid. 1 The cow-bird is a very prolific layer, and 

 it is possible that we may see, in this proceeding, the 

 survival of a means which it once employed to avoid 

 the discomfort attendant on the rearing of too large a 

 family, before it had hit upon a still better way out of 

 the difficulty. The way in which the moorhen carried 

 the eggs is interesting, since it is that employed by 

 ravens in the Shetlands, when they rob the sea-fowl. 

 It would seem, indeed, the only way in which a bird 

 could carry an egg of any size, without crushing it up. 

 As bearing on the strongly developed nest- 

 building instinct of the moorhen, leading it, some- 

 times, to make four or five when only one is 

 required, it is interesting to find that, in some cases, 

 the building is continued all the while the eggs are 

 being hatched, or even whilst the young are sitting 

 in the nest in fact as long as the nest is in regular 

 occupation. The one bird swims up with reeds or 

 rushes in his bill sometimes with a long flag that 

 trails far behind him on the water and these are 

 received and put into position by the other, in the 

 nest. Thus the shape of the nest may vary, some- 

 thing, from day to day, and from a point where, 

 yesterday, the eggs, as one stood, were quite visible, 

 to-day they will be completely hidden by a sconce, 

 or parapet that has since been thrown up. It may 

 be thought, from this, that the birds have some 

 definite object in thus continuing their labours, but, 

 for myself, I believe that it is merely in deference 



1 Hudson's "Argentine Ornithology," vol. i., pp. 72-79. 



