176 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 
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 scrawis 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 Yar- 
rel] (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. 
