1.38 
THK CONDOR 
Vol. XIV 
The geometrical ratio of reproduction of plant,s and animals is large enough 
to necessitate an increase in numbers were it not for adverse circumstances. 
I'or example: The female of each pair of quail, judging from records, lays an 
average of twelve to fifteen eggs. \Trious dangers, however, probably pre- 
vent the hatching of more than an average of ten young. If all of these young 
should survive and reproduce, at the end of the second year there would be 
132 quail for every original pair. But we know that this is not the case, but that 
there is usually about the same number each year. This means that the death 
rate must equal the birth rate, and, in the case of the California valley quail, 
the death rate must be some five times as great as the normal minimum popu- 
lation. Or. in other words, the life rate, or rate of survival, must be only 2 out 
of every 130 quail. 
Taking a covey of 100 quail, probably at least 40 of that number would 
average a brood of ten young each year. This would mean that just after the 
hatching season, there would be something like 500 (|uail where there 
had been 100. At the opening of the tiext breeding sea.son this covey, under 
natural conditions, would have been reduced to the 100 again. Evidently there- 
fore, there would have been a mortality of about 400. There are a great many 
factors to account for this immense mortality, chief among them being, under 
natural conditions, lack of food supply and destruction by predatory mammals 
and birds. 
If we make a hypothetical curve, the points to be brought out are made 
intelligible. If along the left-hand side of the graph are plotted the numbers 
of individuals, and along the bottom, the months of the year, the maximum 
and minimum numbers would form a curve .such as is seen in A. The minimum 
numbers can reasonably be expected to exist just before the eggs are hatched, 
