324 THE NESTS AND EGGS OF BRITISH BIRDS. 



other culminating in rugged precipices full of turfy 

 hollows with a thick covering of loamy soil. It is 

 gregarious during the breeding season, but the colonies 

 vary a good deal in size, the most important and ex- 

 tensive one known to me being on the island of Soay in 

 the St. Kilda group. Many scattered pairs may be 

 met with here and there, but this island seems to be 

 the grand head-quarters of the species in our area, 

 if we perhaps except that on Puffin Island near the 

 Little Skellig. This Shearwater most probably pairs 

 for life, and season by season returns to its favourite 

 breeding-places. The egg is laid in a burrow, usually 

 excavated by the bird, and from four to twelve feet or 

 more in length. These 'burrows are made in the steep 

 grassy parts of the cliff, or near their summit, or on the 

 downs sloping to the water. Many of them are made 

 under large masses of rocks impossible of human access. 

 I found a scanty nest of dry grass at the end of the 

 burrow, but other observers have found the egg on the 

 bare ground. At the entrance of a burrow in use a few 

 droppings are almost invariably seen. The Manx Shear- 

 water sits closely ; in fact, few if any of the birds are to 

 be seen during daylight, no matter how large the colony 

 may be. The sitting bird rarely makes any effort to 

 escape, suffering itself to be dragged out. Many nests are 

 made close together, and sometimes one main entrance 

 will lead to several burrows each containing a nest. 



RANGE OF EGG COLOURATION AND MEASUREMENT : 

 The Manx Shearwater only produces a single egg for a 

 sitting, but if this be removed another will generally be 

 laid. This is pure white in colour, and rather smooth in 

 texture. Average measurement, 2*4 inches in length, by 

 1*65 inch in breadth. Incubation is performed by both 

 sexes, but the period of its duration is not apparently 

 ascertained. 



