Reproduction 105 
ning, presented an appearance no different from this except in 
size (Plate X 
Enemies—Tables of mortality have been prepared which 
give, as far as known, the enemies of nestling Larks as well as 
percentages of loss by season (Tables 22, 23, 24 and Figure 11). 
Enemies early in the season are meteorlogical plus a scanty food 
supply and uneven feeding. Criddle (1920) maintains that early 
nests in Manitoba rarely raise more than one nestling. This is 
in essential accord with the writer’s observations at Evanston 
and at Ithaca. Later enemies are predacious animals chiefly 
and these apparently beset the nestling after heavy vegetation 
has encroached upon the nestling site and so has given the 
TABLE 20 
Growth of a June Prairie a Lark nestling and its Cowbird nest-mate, 
to nest leaving, Evanston, IIl., 1926. 
Weight (in grams ) Length (in centimeters) 
Lark (hatched Cowbird Lark Cowbird 
Seen Kee ae oe June 8) 
gHUe Ge cee 4.1 2.3 
Tne Hh: 6.3 4.5 6.5 5.1 
pe He 10.0 6.6 6.2 5.8 
ee. oe 13.3 9.4 7.0 6.3 
don cack ene Ono 16.6 12.6 7.4 7.1 
muah, oe gee 17.0 14.0 7.6 7.2 
we 17.1 15.3 8.0 7.5 
dnc gt PP eR Oe 20.3 16.8 8.8 7.6 
WUE co G aL -7 18.4 9.2 8.0 
Av. daily increase... . 2.8 2.01 53 41 
nin an RCUSTNC a 
skulkers easy access under cover. The optimum season lies 
between late April and mid-May when weather is more lenient 
but the barren conditions still unaltered. Perhaps the predilec- 
tion of the Lark for open, unobstructed nesting sites has been 
evolved through this protective advantage to the young. 
The loss through improper feeding lies in the fact that incuba- 
tion is begun so frequently before the set is complete; the last 
young to hatch then are at a disadvantage as regards position, 
for they are forced to the rear of the nest. The larger, in front, 
