NON-INDIGENOUS BRITISH BIRDS. 123 



spotted with rich brownish-red. On some eggs the 

 colour is so thickly if somewhat unevenly washed over 

 the entire surface that no ground colour is visible ; on 

 others the markings take the form of blotches and spots 

 amongst which the ground colour shows plainly enough, 

 except on the larger end of the &gg, where the blotches 

 become confluent and form a zone. Occasionally this 

 zone is round the smaller end of the Qgg. Average 

 measurement, 2-6 inches in length by 2*0 inches in 

 breadth. Incubation is performed chiefly by the female, 

 but the duration of the period is unknown. 



Diagnostic characters : The rich colour and size 

 of the eggs of this Vulture prevent them from being 

 confused with those of any other European species. 



Family FALCONID.E. Genus Hierofalco. 



Sub-family FALCONING. 



WHITE JER-FALCON. 



Hierofalco candicans {Gmelin). 



(British : Rare nomadic winter migrant.) 



Single Brooded. Laying season, May and June. 



Breeding area : Northern Nearctic region. The 

 White Jer-Falcon is only known to breed in North 

 Greenland, where it has been noticed nesting as far 

 north as Grinnell Land in lat. 79° 41', and Arctic North 

 America westwards apparently to Alaska and the 

 Asiatic coast of Bering Strait. 



Breeding habits : But little is known of the nidi- 

 fication of this handsome bird, and its habits during the 

 breeding season remain for the most part undescribcd. 



