172 U.S. NATIONAL MUSEUM BULLETIN 237 paet i 



of the wing the second day after hatching. All other tracts, both 

 dorsal and ventral, are well defined by protruding papillae at the end of 

 the fourth day. Those of the head and caudal tracts are the last to 

 appear. 



The growth of the feather papillae is extremely rapid, and by the 

 end of the sixth day those of the wing tract begin to unsheath at the 

 tips. Unsheathing now progresses very rapidly; by the end of the 10th 

 day the exposed tips of nearly all the contour feathers are out of their 

 sheaths. 



The growth of the tarsus, toes, and nails is practically complete 

 when the young leave the nest, whereas the tail, which is more than 

 15 centimeters long in the adult, is less than one-half centimeter in 

 length at this time. The time required for development is closely 

 correlated with the time the bird acquires the use of the respective 

 parts. The legs and toes are called upon to serve the bird the moment 

 it leaps from the nest, but a long tail would be a nuisance in the 

 crowded nest and is not essential as a rudder until flight is attempted. 



The growth of most parts of the bird is rapid until the eighth day. 

 Weight increases in the nest at the rate of almost 2 grams per day. 

 One young that weighed 2.8 grams at hatching weighed 18 grams 

 when it left the nest on the eight day. Growth slows after the young 

 leave the nest; one young bird lost weight. 



Each of 18 dickcissel nestlings of five broods was tagged for later 

 identification. A number of them recaptured from 1 to 6 days after 

 leaving the nest made it possible to complete a series of weights, 

 measurements, descriptions, and photographs through their first 2 

 weeks of hfe. The young, though often at a considerable distance 

 from the nest, were easily located by watching the feeding operations 

 of the adult female. It became increasingly difficult to find them as 

 they acquired the ability to fly or to run rapidly through the grass. 

 A tagged bird 18 days old was collected a mile away from the nest 

 where it was reared, a fact which explains the difficulty in securing 

 later stages of the tagged young. Although the young dickcissel 

 cannot fly when it leaves the nest, it acquires the ability within 2 or 

 3 days, and when about 11 days old is able to fly from 100 to 150 feet. 

 When given the advantage of a start from an elevated perch, some 

 flew even farther at this age. 



The following description of the juvenal plumage is based on a 

 study of the young at about the time they leave the nest. The 

 colors were determined with the use of Ridgway's Color Standards 

 and Nomenclature. While considerable care was exercised in com- 

 paring these colors, they are at best approximations: 



Upper parts buffy brown shading to sepia on the crown; feathers 

 of the back fuscous black edged and tipped with cinnamon buff; 



