64 Trans. Acad. Sci. of St. Louis 
It is probable that, once a nest is started, subsequent cold 
weather will not inhibit it—the physiological processses are not 
checked. To substantiate this observe the weather of March, 
1927, that intervened between the initiation of the nest about 
March 11 and its ultimate destruction at the end, or, again note 
that the nest begun April 6, 1927 (Fig. 8) passed through 
several nights with temperatures much below freezing immedi- 
ately thereafter but the clutch was completed in record time 
(indeed the eggs must have survived this cold uncovered). If, 
then, cold weather alone will not destroy March nests their 
meteorological enemy is restricted to snow. Without a doubt 
the female bird will incubate through a slight snow without re- 
linquishing her eggs. Note that a slight snow fell March 26 
(Fig. 7, also Plate VII, Figures 2), but the nests were not 
abandoned because of this. Many writers have found Lark 
nests in the snow and Langille goes so far as to say that a 
Horned Lark flushed out from under ‘‘three or four inches’’ of 
snow, April 6, 1880 (Langille, 1892), but it is probable that 
the bird would not have remained under the snow for more 
than a few hours. The snows of early April 1926 and 1927 
destroyed all nests and there is no doubt that any snow of 
three inches or more that lasts two or three days will cause 
the destruction of nests. Bendire (1895) in quoting Harris, 
says: ‘‘The weather during the latter part of March (in 
western New York) is often very pleasant and warm, only to 
be followed by a heavy fall of snow about April 1, when a good 
many unfinished nests and incomplete sets of eggs are snowed 
under and deserted by the owners; in fact, only a few birds 
will cling to their nests under these circumstances, as I have 
found many abandoned ones in different seasons.’’ 
Now, having concluded that nests would be begun in March 
whenever two or more days of a mean temperature of 40-49 
degrees F. occurred, and that they would be destroyed by 
snow of three or more inches lasting two or more days, the sue 
cess of hypothetical nesting at Chicago and Evanston coul 
be tabulated from the weather summaries. The only reco 
for snow on the ground in these summaries is at 8:00 P. M. at 
Ithaca or 7:00 P. M. at Chicago and this is exceedingly co 
‘servative as far as the total amount of snow is concerned. The = 
result of this tabulation is shown in tables 1 and 2. The interest- 
