Recently published Ornithological Works. 



159 



the Cuckoo. From Dr. Rey^s evidence it would appear that 

 in Germany the Red-backed Shrike, the White Wagtail, and 

 the Redstart are the favourites, as the eggs laid in these 

 birds^ nests comprise half of the total number of Cuckoos' 

 eggs which have come under Dr. Rey^s notice (24 per cent., 

 14 per cent., and 12 per cent, respectively). Of the 531 

 Cuckoos' eggs observed by Dr. Rey, 180 (or 30 per cent.) 

 resemble in colour the eggs of the foster-parent, and, curiously 

 enough, out of Q7 Cuckoos' eggs found in Redstarts' nests, 

 57 were blue. Dr. Rey attempts to arrange the foster- 

 parents of the Cuckoo geographically ; but as nearly all his 

 Cuckoo-eggs have been collected in Germany, the statistics 

 of the other countries may be passed over as embracing too 

 few examples to yield a correct average. The following 

 analysis of the German examples of eggs laid, with the 

 species, of which he records more than twenty examples, are 

 interesting : — 



Lanius collurio 172 



Motacilla alba loo 



Sylvia liortensis 103 



Troglodytes parvulus 82 



Acrocephalus ariindinaceus . . 71 



Erithacus rubecula 57 



Sylvia cinerea 45 



nisoria 34 



Ruticilla pbosnicurus .... 25 

 Acrocephalus phragmitis . . 25 

 palustris 23 



The list of the various foster-parents of the Cuckoo has 

 now reached to 117 species, but in many cases Dr. Rey 

 admits that the evidence is unsatisfactory. It sometimes 

 happens that two and even in some cases three Cuckoo's 

 effsrs have been found in one nest. In these cases it is 

 generally found that the two eggs are very difiFerent, no doubt 

 being laid by different parents, and in the few cases where 

 they resemble each other it is possible that the similarity 

 may be due to the fact that two different Cuckoos may lay 

 very similar eggs. Dr. Rey admits that the same Cuckoo 

 lays similar eggs year after year. 



Cuckoo's eggs have thick shells. In size they are slightly 

 larger than those of the Crested Lark, but not quite so large 

 as those of the Red-backed Shrike ; nevertheless, they are 

 25 per cent, heavier than the former, and 21 per cent, heavier 



