NON-INDIGENOUS BRITISH BIRDS. 95 



It Is difficult to say the number of eggs usually pro- 

 duced by each individual Cuckoo every season, but 

 sometimes as many as four are laid in the same nest 

 (whether by one female or several is not known), but 

 usually only two, and in some cases but one. They are 

 pale bluish-green in ground colour, spotted and blotched 

 with pale brown, and with underlying markings of lilac- 

 gray. They are subject to some local variation, but to 

 nothing near the extent presented in the eggs of the 

 Common Cuckoo. On some varieties the surface spots 

 are small and few, but the underlying markings are 

 numerous and conspicuous ; on others most of the 

 markings are collected in a zone round the larger end of 

 the ^%%, and take the form of streaks and scratches with 

 a few spots between. The markings on most eggs are 

 pretty generally distributed over the surface, but are 

 slightly more numerous round the larger end. Average 

 measurement, V2 inch in length by "92 inch in breadth. 

 Incubation is performed by the foster-parent, but the 

 duration of the period is unknown. 



Diagnostic characters : The eggs of this Cuckoo 

 very closely resemble certain types of those of the 

 Common Magpie, but are readily distinguished by their 

 smoother grain, greater rotundity, smaller size, and 

 reddish-brown (not olive-brown) surface spots. 



