I9i7'l Breeding-habits of the Cuckuo. 193 



(4) In addition to Phcenicurus phmnicurus (Common Red- 



start) and Frinyilla moutifringilla (Brambling), in 

 whose nests the Cuckoo's egg almost invariably 

 resembles those of the foster-parent in colour and 

 markings, those in the nests of Sylvia communis (Com- 

 mon Whitethroat), Sylvia simplex (Garden-Warbler), 

 Acrocephalus arundhiaceus (Great Reed- Warbler), 

 and Acrocephalus palustris (Marsh -Warbler), are 

 comparatively often of the same type. In the case 

 of all other species the resemblance is much more 

 occasional, and apparently never occurs in the case 

 of Troglodytes troglodytes (Wren), Accentor modu- 

 laris (Hedge-Sparrow), and the genus Phylloscopus 

 (Chiff-chaffs and Willow- Warblers). 



(5) A resemblance to the actual eggs in the nest does not 



often occur, even in the cases of the Redstart and 

 the Brambling. 



(6) Most female Cuckoos deposit their eggs in the nests 



of that species by which they themselves were reared, 

 and only entrust them to other species when forced 

 to do so, and then only to such as build similar nests. 



(7) Most female Cuckoos deposit their eggs in nests in 



the same, and often rather restricted, locality. 



(8) Neither the ovary nor the development of the eggs 



displays any abnormality in comparison with those 

 of other species. 



(9) The Cuckoo lays some twenty eggs each year. Possibly 



it is this high number which compels her to entrust 

 them to other species. 

 (IQ) Laying takes place on alternate days. 



(11) Normally each Cuckoo lays eggs of the same, or 



virtually the same, variety all its life. 



(1 2) Only one egg is placed in any one nest. 



(13) If two or more eggs are found in the same nest they 



have been placed there by different females. 



(14) The laying period corresponds to that of the foster- 



parents, and differs considerably in different localities, 

 both in duration and date. 



SER. X. VOL. V. O 



