AUKS AND GUILLEMOTS. 



71 



increasing cackling and din. The birds, circling in the air, soon settle again on the 

 stones of the mountain slopes, where, squabbling and fighting, they pack themselves so 

 close together that from fifteen to thirty of them may be killed by a single shot. 

 Their food, which they secure by diving, consists of crustaceans and worms. The 

 single bluish-white egg is laid on the bare ground without a nest, so deep down among 

 the stones that it is only with difficulty that it can be got at. 



FIG. 32. Plautua impennis, great auk. 



The three genera, Uria, Alca, and Plautus, like the foregoing, black with white 

 breast and belly, and white fore-neck during the winter, constitute another group 

 characterized by their more or less compressed bills, upon which the feathering of the 

 head protrudes quite a considerable distance. The first-named genus contains the two 

 different species of guillemots, murres, or lomvias ( V. troile and U. lomvia) repre- 

 sented in the Pacific and Atlantic Oceans by separate varieties, particularly remark- 



