136 Darwin a:id Romanes dealt with. 



XVI. 



The analogy with America here is strong. Several 

 of the American birds will not receive the cuckoo's 

 eggs. One of them is Bullock's oriole : she rids her- 

 self of the cuckoo's egg by at once throwing it out, 

 and not resting till she has done so. 



Another observation of Mr. Gurneys, faithfully re- 

 corded, suggests yet further and more indirect means 

 of promoting their own chances for foster-parents on 

 the part of cuckoos. 



He writes : 



" On the 20th of May, 1897, my son and I were in 

 the pursuit of swallow-tailed butterflies on Sutton 

 Broad, when three cuckoos passed me, one behind the 

 other, probably a hen and two cocks. After flying 

 over a small bog-myrtle or sweet gale bush, not more 

 than two feet high and six feet long, standing by 

 itself on the fen, they betook themselves to an adjoin- 

 ing field. In three or four minutes my suspicion was 

 aroused by one cuckoo returning, which, not heeding 

 me, entered the bush where it remained, but though 

 drawing near very cautiously, I could not see it there, 

 small as it was. When at length the cuckoo had gone, 

 a minute search revealed nothing, and we were just 

 going away, when some ten feet from the bush, the 

 marshman nearly trod on a new yellow wagtail's nest 

 in the grass. It was empty, but scattered round were 

 five young wagtails, quite a week old, the furthest one 

 six feet off, the others nearer, no doubt dropped 

 where we now saw them by the cuckoos. I can only 

 come to the conclusion that this was a cuckoo which 



