eon 
Reproduction 101 
expected, growth in length shows no lessening between the sixth 
and eighth days but rather an acceleration (see Figure 14). 
This is due to the advent of the tail. The retarded or lost young 
noted in the figures are, for the most part, the result of starva- 
tion through poor feedings and scanty food supply. The poor 
showing of the April nestling (see Figure 12) is an exaggeration 
of the situation that prevailed (though usually to a less degree) 
in most April nests. It is the result of two things: (1) pre- 
vailing low temperature and the consequent necessity of much 
Figvro 12 
7 a : : 7 7 3 a 
Fig. 12. Growth in weight of an April set of Prairie Horned — 
nestlings (nest By, April 21 to May 2, inclusive, Ithaca, N. Y., 
1927), 
brooding, hence lessened feedings (see Figure 16) and, (2) an 
apparent lower supply of food. 
Attention should be called to one more point. In the general 
averages (Table 21) the lessened growth in weight and lessened 
increase in length between the tenth and twelfth days is due to 
the fact that birds in the nest at these ages are almost certain 
to be those retarded or improperly nourished, the most pros- 
Perous having gone on the tenth. 
Descriptions of young at various ages——The young in ju- 
venile plumage have been described repeatedly, but apparently 
42 
