@ 
186 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 
four extremes measure 90 by 52, 84 by 54, and 69.5 by 42.5 milli- 
meters, 
Young.—This species has been reported as raising two broods in a 
season, but this is undoubtedly an error due to the prolonged breed- 
ing season on account of frequent robbing. Mr. W. Otto Emerson 
gives the period of incubation, in which both sexes share, as 28 days. 
The young remain on the ledges where they are hatched until ab6ut 
half grown and are, at least partially, fledged in their soft juvenal 
plumage, but they are induced by their parents to take to the water 
long before they can fly. Mr. Finley (1905) gives the following 
graphic account of the behavior of the young murres and their 
brooding parents: 
Where it was a little noisy during the days of incubation, it was the triple 
extract of bedlam turned loose when the murres had young. We tried the 
same experiment of scaring the birds from the ledge and watched their return. 
The young kept up a constant squealing from the time the old birds left; a 
noise that had the penetration of an equal number of young pigs that had just 
been roped and gunney sacked. When the first old hen returned and lit on the 
edge, she bowed elaborately and started calling in cries that sounded, at times, 
just like the bass voice of a man and varied all the way up to the cackling of 
an old chicken, After sitting there for five minutes, she straddled up a few 
steps and started in from the beginning again. Some of the young came wad- 
dling down to meet their parents, calling all the time in piercing screams. 
One crawled hurriedly down to. get under the old murre’s wing, but she gave 
him a jab that knocked him clear off his feet, and sent him looking for his 
real mamma. She looked at two more that sat squealing, but passed them by 
and knocked another one sprawling out of her way. At last a chick came up 
that seemed to qualify, for she let him crawl under her ‘wing. The same thing 
seemed to be going on in every part of the ledge; I didn’t see an old bird that 
accepted a chick until after calling and looking around for from 5 to 20 minutes. 
If the difference in size, shape, and color helps the murre to recognize her own 
egg, then the great variation in pitch, volume, and tone of the voice surely 
helps her to know her own child among so many others. 
As soon as the young murre reaches the water it swims away with 
its parents, often to a long distance from its birthplace. Prof. 
Leverett M. Loomis (1895) says that at Monterey— 
young birds, unable to fly and under the care of adults, appeared early in 
August, probably from a rookery somewhere in the vicinity of Point Santa Cruz, 
These young birds were expert divers. When an adult and its charge were 
approached the young bird would dive first. If the two became separated the 
old one would call loudly and as soon as the young responded the old bird 
would dive, coming to the surface at the spot where the young one had taken 
refuge. 
Mr. Andrew Halkett (1898) saw a murre “one day when hun- 
dreds of miles from land, on the surface of the waves with her 
brood, which consisted of a single young one.” 
Plumages.—I have been puzzled to find any constant characters by 
which the downy young of the two species of murres could be dis- 
tinguished and between the two subspecies of each there is probably 
