Jan. 292% 19 
A HUNTER’S NOTES ON DOVES IN THE RIO GRANDE VALLEY 
By ALDO LEOPOLD 
percentage of squabs of about 400 Mourning Doves (Zenadura macroura) 
killed during the hunting season in the central Rio Grande Valley near 
Albuquerque, New Mexico. The data has been plotted to show percentage of 
squabs killed at weekly intervals from August 16 to December 15, and also the 
average weight, old birds and squabs separately, for the same period. The data 
is as yet insufficient as a basis for smoothed curves, but it is sufficient basis 
for tabular expression as follows: 
S INCE 1917 I have kept a record of weights, food, plumage, habits, and 
Date Percentage Weight Weight 
of squabs old birds squabs 
Aug. 16 ANCL Wh Ble te tate: ee eee 
Aug. 23 1S ee ey 4 A oo 5 gay NR etl Dee. SR ee eee 
Sept. 1 . 55 4.4 Oz. a1 OZ. 
Sept. 8 60 4.3 3.6 
Sept. 15 50 4.2 oe 
Sept. 23 50 4.2 3.4 
The table shows first of all that there are few squabs abroad on the shoot- 
ing grounds until September, and that therefore the old opening date of August 
16 was too early. It shows that the present opening date of September 1 is 
biologically correct. The explanation of the rapid increase in squabs about 
September 1 appears to be as follows: The main crop of squabs stays near the 
nests in the cottonwood bosques and in the foothills, until well grown. The 
adults, however, make long flights to wheat stubble, where most of the August 
shooting used to be done. This August stubble shooting was wrong, because it 
killed mostly birds with dependent young. 
The table shows secondly that after the main squab crop has issued forth, 
the young birds are just as numerous, or slightly more so, than the adults. 
The yearly wmcrease rs therefore about 100%. This conclusion is nearly ines- 
capable, because there are no other factors that I know of which would prevent 
‘the proportion of squabs in the bag from pretty accurately reflecting the pro- 
portion of squabs in the whole dove population. The only possible sources of 
a differential proportion of squabs would be: (a) Selection in shooting. Nearly 
all these birds were killed in pass and jump shooting, and the young birds are 
practically as hard to hit and to kill as the old ones. (b) Wildness. The 
squabs may “‘lay’’ a little better than the old birds, but on the usual clear days 
in normal cover both lay good enough to prevent an abnormal percentage of 
squabs in the bag. (c) Distribution of young and old birds. The data covers 
a wide variety of sites, seasons, hours, feeds, ete., and there could be no differ- 
ential from these sources. (d) Differential migration. The general accuracy 
of the conclusion above stated could be impaired only by assuming a differen- 
tial migration of young as compared with old birds. There is some evidence 
to show that the grown squabs of the main crop go south before the late squabs 
and old birds (see decrease in average weight of squabs and percentage of 
squabs during September). However, to admit this as material to the ques- 
tion of yearly increase would raise rather than lower the estimated annual in- 
crease of 100%, and it seems nearly incredible that a bird which lays only two 
eggs could more than double its numbers each year. In fact, even the 100% 
