460 THE CUCKOO 



the British Isles after the middle of July : . the majority of the young birds leave 

 in August, but a fair proportion do not emigrate until September (cf. Gladstone, 

 loc. cit. ; Nelson, loc. cit. ; Ussher and Warren, loc. cit. ; and B. O. C. Migration 

 Reports, v. p. 270). From among the various exceptional records for later dates 

 we may cite the outstanding case of a cuckoo reported from the Pentland Skerries 

 (off Caithness) on 7th November 1906 (cf. Paterson, Annals Scot. Nat. Hist., 1907, 

 p. 143). Similarly, on Heligoland, where the spring passage takes place chiefly in 

 May, the adults' return passage takes place in June, and the young birds' in July 

 and August, a space of from three to six weeks intervening (cf. Gatke, Vogelwarte 

 Helgoland, Eng. trans., 1895, p. 423). The cuckoo is at least partly a nocturnal 

 traveller, and it is frequently obtained at the light stations (cf. Nelson, loc. cit. ; 

 and Ussher and Warren, loc. cit.). It is also mainly a solitary migrant, but it is 

 occasionally seen in flocks at the migration season, and one numbering " several 

 dozens" has been recorded (cf. Gladstone, op. cit., p. 168. See also Nelson, B. of 

 Yorks., p. 288 ; and Zoologist, 1845, 821). [A. L. T.] 



4. Nest and Eggs. As is well known, the cuckoo makes no nest, but is 

 parasitic upon other species of birds. As far as we know at present the female 

 cuckoo is polyandrous, and produces, according to Saunders, from 5 to 8 eggs in the 

 season. The researches of the late Dr. Rey and others on the Continent, however, 

 tend to prove that a much larger number is produced, estimated by Rey at about 20, 

 laid on alternate days, and deposited as a rule in nests of the same species, from 

 which one or two eggs are generally removed. Capek is however probably nearest 

 the truth in saying that the eggs are laid on alternate days in two clutches, the 

 first of 5-7 eggs, and the second, after an interval, of about 4 or 5. In the case of 

 small birds at any rate the egg is laid on the ground and afterwards inserted in the 

 nest by the bill. In colour and markings the eggs of the cuckoo vary considerably, 

 but it is a curious fact that the range of variation in the British Isles is consider- 

 ably less than on the Continent. Many resemble tolerably closely the eggs of the 

 foster-parents, but there are notable exceptions to this rule, the blue eggs of the 

 hedge-sparrow being often associated with cuckoo's eggs of a totally different type. 

 It is impossible in a brief space to describe all the different types which occur, and 

 a glance at the plate will give a better idea than pages of description. Most 

 British eggs vary in ground-colour from reddish, purplish, bluish, greenish to 

 yellowish or brownish grey, and are mottled, clouded, and spotted, sometimes closely 

 and at other times sparingly, with darker markings of various shades. Only one 

 egg is placed in each nest, cases in which two or even three eggs have been found 



