38 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



The measurements of 135 eggs in the United States National Museum 

 average 28.02 by 20.44 millimeters ; the eggs showing the four extremes 

 measure 32.8 by 19.6, 25.9 by 22.4, 25.2 by 20.1, and 25.9 by 18.8 

 millimeters.] 



Young. — From a comprehensive, carefully prepared study of the blue 

 jay, a thesis for the degree of doctor of philosophy, sent to Mr. Bent 

 in manuscript by John Ronald Arnold, the following observations are 

 abstracted: The period of incubation was found to be 17 or 18 days in 

 the vicinity of Ithaca, N. Y., and 17 days in New Jersey. The young 

 at the time of hatching were limp, blind, and entirely naked. When 

 3 hours old they were able to raise their heads to the rim of the nest. 

 By the fifth day the eyes were just beginning to open, and the birds 

 grasped the lining of the nest with their claws. "During the eighth and 

 ninth days the feathers in all the body tracts except the head and neck 

 regions begin to break from their sheaths." By the seventeenth day the 

 nestlings begin to resemble a blue jay and are almost ready to leave the 

 nest. They leave 17 to 21 days after hatching. 



In close agreement with these dates, Isabella McC. Lemmon (1904) 

 gives the incubation period between May 2 and 19 and reports that the 

 young flew on June 6. 



Donald J. Nicholson (1936) writes, referring to the young Florida 

 blue jay : 



They leave the nest in from fifteen to eighteen daj's, at which time the tails 

 are quite short, and the feathers not fully developed on any part of the body or 

 v/irgs. Their power of flight is not by any means strong when they first leave 

 the nest, and only short spaces can be covered. Many a young bird at this time 

 of the year falls an easy prey to cats and various snakes. * * * 



In three weeks to a month, it is difficult to distinguish the young from the 

 adults, but the face and throat is a smoky, dark color, instead of the rich black 

 of the adult, and the bill is horn-colored, instead of black as in the parents; 

 otherwise the plumage is apparently the same to all outward appearances. By the 

 following spring no difference is seen. Even by fall I can not discern a particle 

 of difference. A fledgling when caught, if caught by anything, emits terrified 

 screeches as if in mortal agony, bringing the parents to its defense at once. 



Apparently the voice develops early; I have heard a young bird on 

 leaving the nest shout almost as loudly as its parents. 



Francis Zirrer has sent us the following note: "Although considered 

 more or less a raptor, the young blue jay must learn about the various 

 small game before it will touch it. At our woodland cabin we were 

 greatly annoyed by various species of wild mice, especially Peromyscus. 

 Throughout the winter many were caught and deposited on the feeding 

 table in the morning. We noticed, however, that the majority of the 

 blue jays, apparently the young birds of the previous summer, were 



