186 BXTIXETIN 107, UNITED STATES NATIONAL MUSEUM. 



four extremes measure 90 by 52, 84 by 54, and 69.5 by 43.5 milli- 

 meters. 



Totmg. — 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 about 

 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 difCerence 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 exjwrt 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." 



Plmnages. — 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 



