39G Bulletin of the British 



'' 2. The most important characters of the eggs of Cucnlus 

 canorus are their form, the weight of their shells, and 

 above all their thickness and hardness. 



" 3. The majority of the eggs of Cuculus canorus resemble 

 in colour and markings the type o£ one of onr common 

 Passerine Birds ; while some show a kind of mixed 

 type, and some do not exactly resemble any known 



" 4. The eggs laid in the nests of Ruticilla j)hcenicurus 

 and Fringilla niontifringilla are nearly always like 

 those of the nest-owners in colour and markings 

 (57 out of 67 in those of the former, and all in those 

 of the latter). Imitations are also common in nests 

 of Sylvia cinerea, Sylvia hortensis, An'ocephalus 

 streperus, and A. phragmitis, while they are rare in 

 others, and have never yet been found in nests of 

 Troglodytes parvulus, Accentor modularis, and the 

 different Phylloscopi. In most countries it may be 

 said that there are many more Cuckoos^ eggs which 

 do not imitate those of other birds than those which 

 are successful imitations. 



" 5. Most Cuckoos are in the habit of placing their eggs in 

 nests of one species of bird, and take to other nests 

 only if they cannot find their habitual nests. 



" 6. They use, as a rule, one and the same district (mostly 

 very limited) for depositing their eggs year after 

 year. 



"7. Neither the ovary nor the development of the eggs of the 

 Cuckoos differ in atiy way from those of other birds. 



" 8. The female Cuckoo lays about 20 eggs every year, and 

 these are laid on alternate days. 



" 9. Each female Cuckoo lays similar eggs during its life. 



' 10. Each female lays only one e^^ in one nest. If more 

 than one be found they invariably belong to diflerent 

 females. 



'11. The time when the females lay varies greatly. 



' 12. The female removes, in most cases (but not always), 

 some of the eggs of the nest-owners.^'' 



