176 LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS 



Eggs. The murre lays a single egg, which varies in shape from 

 "ovate pyriform" to "elliptical ovate" or "elongate ovate," with a 

 decided tendency toward the more pointed form. The shell is thick, 

 rather rough, and without luster; the egg is very tough and fortu- 

 nately not easily broken, as it receives very rough usage. The eggs 

 are not distinguishable from those of the other American species of 

 Uria, and they are subject to almost endless variations in color and 

 markings. The ground color shows a great variety of light blues, 

 light greens, and intermediate shades, with all the paler tints down 

 to pure white; these blue and green eggs are the commonest types; 

 the less common types vary from "vinaceous tawny," "pinkish buff," 

 or "cream buff" down to white. Some eggs, particularly the palest 

 types, are entirely spotless, but the great majority of them are more 

 or less heavily and conspicuously marked in an endless variety of 

 patterns, finely speckled, deeply clouded and washed, heavily and 

 boldly blotched or beautifully scrawled in fantastic patterns of two 

 or three colors. Most of the markings are in the darkest shades 

 of brown or sooty black, but some are in the brighter or lighter 

 shades, such as "bay," "chestnut," "burnt umber," or "sepia." Many 

 eggs show lines and scrawls of olive shades, light browns, drab, 

 lilac, or lavender. The eggs are usually handsome, and a large series 

 of them makes a striking display. The measurements of 64 eggs in 

 the United States National Museum average 81 by 50.5 millimeters; 

 the eggs showing the four extremes measure 89 by 50.5, 84 by 54.5, 

 and 66 by 44 millimeters. 



The period of incubation is given as from four weeks to one 

 month. Both sexes assist in this duty and the male usually stands 

 beside the female while she is incubating, except when he finds it 

 necessary to go to sea for food. The incubating bird sits horizontally 

 upon the egg, as other birds do, and not standing up straddling it, 

 as some writers have stated. The following quotation from Yarrell 

 (1871) is interesting: 



It may be accepted as a fact that each bird recognizes its own egg, for 

 Messrs. Theodore Walker and G. Maclachlan marked a number of birds on 

 the ledges at Barra Head by splashing red paint over them, and the same 

 individuals were found at their accustomed post day after day. Mr. Seebohm 

 says that, at Flamborough, Lowney the veteran cliff climber is of opinion that 

 if the egg is taken the same bird will lay a second about nine days later, and 

 this agrees with the experience of Mr. Maclachlan; but if the second egg is 

 taken the bird lays no more that season. If undisturbed, the same birds re- 

 turn year by year to the same ledge and deposit their egg in the same spot, 

 but if the eggs are taken the birds will shift their ground; it may be only to 

 the next ledge. It is also pretty well established that the same bird lays a 

 similar egg year after year. 



Young. The young are fed by both parents, at first on semi- 

 digested food, but later on small fishes and other marine animals. 



