SPARROWS, TROUT, AND BREEDING 267 



to cuckoos which make use of the hedge-sparrow as foster- 

 mother escape detection both by boys and the foster- 

 parents, and successfully hatch out and propagate the 

 race of blue-egged cuckoos with a memory and a sense of 

 smell which bring them back if they are hen-birds to the 

 little hedge-sparrow's nest when they are grown up and' 

 have an egg to dispose of. The spotted grey or brownish 

 eggs are, if not discovered by boys, ejected (there is reason 

 to believe) by the hedge-sparrows themselves. They were 

 deposited by mistake by some pippet-loving or warbler- 

 seeking strain of cuckoo in a hurry, or are throw-backs 

 to a common ancestral colouring of the egg due, perhaps, 

 to the male parent not being of the true blue strain. A 

 very fine series of " clutches " and nests of hedge-sparrow, 

 robin, shrike, reed-warbler, pippet, yellow-hammer, and 

 other birds with the accompanying cuckoo's egg may be 

 seen in the Natural History Museum, and they show how 

 closely the parasitic egg often resembles that of the foster- 

 parent, though striking failures also occur. 



The hedge-sparrow is placed in that group of small 

 birds which includes the robin, the thrushes, and the 

 warblers; it is not a finch. On the other hand, the 

 house-sparrow is a finch, allied to the chaffinch, the gold- 

 finch, and the brambling. It has, like all the finches, a 

 very powerful broad-based beak, and is more than a 

 match for bigger birds than itself. It is really a parasite 

 or " commensal " (messmate) of man, living and flourishing 

 entirely by helping itself to the grain and the young 

 buds of shrubs grown by man, and in towns to the waste 

 fragments of his food and the grain left in horse-dung. 

 Whether it does any good in the early part of the year by 

 eating grubs seems to be doubtful, but the conclusion is 

 justified that it does more harm than good, especially as 

 it drives away other small birds which are exclusively 

 insectivorous. It has gone with European man to all 



