3i6 THE NESTS AND EGGS OF 



large and boldly defined, mostly situated on the major 

 half of the ^<g% ; another type is sparingly spotted, 

 chiefly on the major half; another type is beautifully 

 and intricately pencilled and streaked over most of the 

 surface. Average measurement, 4*9 inches in length, by 

 2"8 inches in breadth. The duration of the period of 

 incubation is unknown, as is also which sex performed 

 the duty. 



Diagnostic characters : The size, .shape, and 

 general colouration of the eggs of the Great Auk are 

 sufficiently distinctive to prevent confusion with those of 

 any other known species. 



Family PROCELLARIID^. Genus Bulweria. 



BULWER'S PETREL. 



Bulweria columbina {Moquin-TandoJi). 



(British : Very rare abnormal spring migrant.) 



Single Brooded probably. Laying season, May and June. 



Breeding area : Northern Circumtropical Seas. 

 Bulwer's Petrel is only known to breed on the Canaries, 

 Madeira, and Porto Santo Islands, on the Sandwich 

 Islands, and on the Volcano Islands. 



Breeding habits : Bulwer's Petrel is an oceanic 

 bird, and only resorts to the land to breed. Its 

 favourite nesting places are isolated island groups with 

 a good ocean aspect. This bird probably pairs for life, 

 and resorts to certain spots each season for breeding 

 purposes. No nest is made, the ^gg being laid in 

 hollows under rock fragments, or beneath large stones 



