LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS. 85 
Mr. Dawson (1909) says: 
A 45-degree slope of soil is the characteristic nesting site of the puffin. Here 
tunnels are driven at random to a depth of 8 or 4 feet, and so close together 
that once, on Erin, by placing a foot in the entrance of a burrow and fetching. 
a compass, I was able to touch with the hands the entrance of 25 others, ap- 
parently occupied. This may have been an unusually populous section, but 
reckoning at half that rate, an acre of ground would carry 2,700 burrows. 
Hard or rocky soil is not shunned in prosperous colonies, but many efforts here 
are baffled outright and “ prospects”’ are at least as numerous as occupied bur- 
rows. Elsewhere the top soil on precipitous, clinging ledges may be utilized, 
or else crannies, crevices, and rock-hewn chambers. 
The tufted puffins have always been one of the interesting features 
of the famous Farallone Islands and their nesting habits there have 
been described by various writers. Here they seem to prefer to nest 
in the crevices in the cliffs and in cavities under the bowlders which 
form natural burrows from 2 to 5 feet in depth. Sometimes crude 
nests are made of coarse, dry weeds, but more often there is no at- 
tempt at nest building. 
Eggs.—This puffin lays but one egg, which is usually “ovate” in 
shape; some specimens are more pointed, with a tendency toward 
“ovate pyriform.” The shell is thick and lusterless. The color is 
very pale bluish white, or dull, dirty white. Many eggs show a few, 
and some numerous, spots or scrawls of various shades of gray or 
pale brown, which sometimes form a ring around the larger end. 
The measurements of 48 eggs in the United States National Museum 
and the writer’s collections average 72 by 49.2 millimeters; the eggs 
showing the four extreme measure 78 by 50, 73.5 by 51.5, 65.5 by 
49.5, and 68.5 by 45 millimeters. 
Young.—Apparently two broods are raised in a season, at least in 
the southern portion of its breeding range, for eggs are found in the 
Farallone Islands early in May and fresh eggs are found again early 
in July. Mr. W. Otto Emerson states positively that two broods are 
raised and gives the period of incubation as 21 days. Both sexes in- 
cubate. Mr. Emerson says that they take turns at the duties of in- 
cubation every 12 hours, relieving each other at night and morning. 
Each bird spends a part of the day or night at sea in search of food, 
but, when not so occupied, it may be seen standing like a sentinel 
at the entrance of the burrow, waiting to relieve its incubating mate. 
Mr. Emerson says: 
The young are fed in the burrow until fully feathered and large enough to- 
take care of themselves in the sea water. The food of the young consists of 
shellfish, mussels, sea urchins, small smelt, sardines, herring, and perch. 
The young puffins are gluttonous feeders and will gorge them- 
selves with food until they can hardly move. They are also very 
pugnacious, fighting among themselves and biting at anything that. 
comes within reach. 
