218 Major R. F. Meiklejohn on the [Ibis, 



There is also a case on record of a White Wagtail's nest, 

 built in a fairly deep hole in a tree with a rather narrow 

 entrance, which only contained a young Cuckoo, and as it 

 seemed out of the question for the latter to have ejected the 

 other inmates itself, it must be assumed that the parent had 

 assisted. It thus seems clear that the female Cuckoo, at all 

 events occasionally, does take an interest in the subsequent 

 fate of its egg. 



Finally, I once found a Cuckoo's egg in a Hedge- 

 Sparrow's nest, and, on blowing the eggs, discovered that 

 the former was considerably more incubated than the 

 others, which were nearly fresh. Tliis I can only explain 

 by the theory that the Cuckoo at times changes her egg 

 from one nest to another, possibly for reasons of safety. 



Summary. 



Having, then, dealt with the main theories and con- 

 clusions concerning the breeding-habits of the Cuckoo, 

 the results I arrive at are as follows, those based on theory 

 being marked with an asterisk : — 



1. *The Cuckoo is probably polygamous. 



2. The eggs vary more in colour and markings than those 

 of any known species. 



3. Their main distinctive features are the comparatively 

 greater weight, thickness, and strength of the shell. 



4. Most Cuckoos' eggs resemble the normal type of those 

 of a certain number of the species which are usually selected 

 as foster-parents ; others are of a " mixed type," inter- 

 mediate between two such species or of a " distinctive 

 type " of their own. The percentage of eggs exactly 

 resembling those of the clutch in which they are found 

 is only about 13 per cent., while those resembling the 

 general type of the species in whose nest they are found 

 amount to some 45 per cent. 



5. The resemblance occurs most often in the cases of 

 the Common Eedstart, Brambling, Whitethroat, Garden- 

 AVarbler, Reed- Warbler, Marsh-Warbler, Sedge- Warbler, 



