
In order to gain information on the habits of birds, considerable time 
was spent in marking individuals so that they could be readily recognized 
in the field. Most of this work dealt with the marking of broods in order 
to study the relations of the nest to brood water. This was done mainly by 
marking the young with aniline dyes injected into the egg as described by 
Evans (1951). In addition to this, hens were trapped at the nest and marked 
on the wings with airplane dope to give a larger number of combinations so 
that more individuals could be identified without possibility of confusion. 
This method has been described by Sowls (1950). 
Considerable time was spent developing a method for capturing breeding 
adults during the courtship and nesting period so that they could be marked 
for recognition. The method was based on a modification of the cannon- 
projected net trap described by Dill and Thornsberry (1950). 
An outfit was made up using two cannons similar to those of Dill and 
Thornsberry, but using black powder as a propellant and a black powder 
electric squib as the "primer" (Black and Evans, 1953). 
The trap was set up on the margin of a pothole facing out over the water 
with the net just at the water's edge. Baiting with food was ineffective 
during the nesting season, and as a means of localizing birds in front of the 
trap, @ log about 2 feet long was set out at each trapping site about in the 
center of the extended net. The log served as an attractive loafing site for 
the birds and as an aiming point for determining when to fire on birds cruising 
along the shore. 
In 1952, eight blue-winged teal and a mallard drake were captured and 
marked with model-airplane dope. Better equipment in 1953 led to the capture 
and marking with plastic neckbands of 17 blue-winged teal. Considerable 
difficulty was experienced in locating the marked birds and only 157 observa- 
tions were made. Of the 26 birds marked, 6 were never seen again. Observa- 
tions of the remaining 20 indicated that it was unlikely they were frightened 
from the area by the cannon, as many were disturbed so little that they re- 
turned to the trapping area within a day or two of their capture. These six 
birds not subsequently observed were probably either not yet settled on the 
area, or were captured at the extreme edge of their range. 
Analysis of production 
Each square mile of the area was censused for broods at least once every 
35 days and it was assumed that all broods were counted. The main difficulty 
in getting a reliable figure lay in the elimination of duplicate counts of 
individual broods that moved from pothole to pothole. This was done by care- 
fully aging all broods seer and eliminating from the tally all those old 
enough to have been tallied on a previous count. The method is described in 
Blankenship et al. (1953). 
Information on the ages of all broods on the study area was used not only 
for determining the production of young, but also for working out the chronology 
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