62 Trans. Acad. Sci. of St. Louis 
word has been said in any given case. This problem still re- 
mains one of the greatest, most fascinating enigmas of ornithol- 
ogy. Nor is there an adequate explanation for a March nest 
in the case of Otocoris alpestris praticola. If the bird nested in 
March only then the case would be clear for the argument that 
the barren nesting site is required—but it finds barrens into 
July; if it were true that greater food opportunity existed in 
March and not in other months there would be a good cause for 
nests at that season—but many young die of starvation even in 
April (see tables 22,23) ; the argument that the season is early 
because the bird arrives early is good but so does the Gold- 
finch and the Waxwing, and they delay to late June or early 
July before starting; the physiological cycle is at the bottom of 
it but why such a cycle? Why nestings that are snowed under 
in March when the season extends to July? 
Before going further with an attempt to explain this phe- 
nomenon I wish to present a study of the possibilities of suc- 
cess of March nests in two localities of their range. By a strange 
coincidence the March nests at both Illinois in 1926, and at Ithaca 
in 1927, were destroyed by a heavy snow late in that month 
and early in April. From these two observations I was led to 
believe that the majority of March nests, at these latitudes, 
would be unsuccessful. To prove or disprove this I obtained 
weather summaries running back to 1910 for the Chicago re- 
gion, and to 1916 for the Ithaca region. 
Weather control of March and April nests.—TFirst, however, 
by a study of known March and April nestings, it was possible 
to learn the temperature and duration of that temperature 
that was required before a nest would be started. This led 
to a very remarkable discovery( see Figures 5, 6, 7, 8) namely, 
that the initiatory temperatures was a mean somewhere be- 
tween 40 and 45 degrees Fahrenheit and that with one exception 
it extended over a period of more than two days. The excep- 
tion was an April nesting which was begun the first day the 
mean was above 40 degrees F., but even here two birds, one of 
which was known to have nested in March, did not begin their 
renesting until the second warm peak when the mean was again 
above 40 degrees F’. and for several days in succession. Knowing, 
thus, what conditions are necessary to initiate a March nest, it 
ey became necessary to consider what conditions will destroy 
