WINTER 
The annual winter survey to obtain in- 
formation on waterfowl wintering conditions 
and distribution covered all major wintering 
areas of the United States, Canada, and 
Mexico. In the State of Alaska and in 
Mexico the Bureau of Sport Fisheries and 
Wildlife organized and conducted the survey. 
In the rest of the continental United States, 
the Bureau organized the survey, but much 
of the field work was done by personnel of 
the various State conservationdepartments. 
The U. S. Department of Defense and the 
U. S. Coast Guard supplied the aircraft used 
in aerial counts in many areas. In 
Canada, the survey was organized by 
the Canadian Wildlife Service and field 
work was done by the Service and the 
Provinces. 
The wintering areas were surveyed by 
means of boats, cars, and aircraft, with 
most of the important areas being censused 
from the air. Aerial photographs were taken 
to supplement visual estimates in some of 
SURVEY 
the more important concentration areas, 
particularly in California. 
It must be emphasized that the number of 
birds observed and recorded during the 
winter survey does not constitute an esti- 
mate of the total population in any Flyway 
or for the continent as a whole: all winter- 
ing areas of North American waterfowl are 
not surveyed and inherent variables exist 
in the estimating technique. However, with 
consistent coverage from year to year in 
the bulk of the wintering areas, it is believed 
that yearly data for most of the major 
species can be used to establish broad 
trends in population size. In addition, the 
winter survey data have great value for de- 
termining the use made of various wintering 
areas and the change in distribution from 
year to year inresponse to changing weather 
and habitat conditions. 
Table C-1 (p. 61) summarizes participa- 
tion by the various groups in the 1961 
winter survey. 
BREEDING GROUND SURVEY 
Surveys are conducted each year on the 
waterfowl breeding grounds for the purpose 
of estimating the relative size of the fall 
flight from each of the breeding areas. Two 
coverages of the breeding areas are re- 
quired to obtain the necessary information: 
the first coverage is made during May and 
June to measure the distribution and rela- 
tive size of the breeding population; the 
second during July to forecast the relative 
number of young that would be produced. 
In July it is necessary to make a pre- 
liminary estimate or forecast of the number 
of young that will be produced, since at 
the time field work must be terminated to 
have the data available for use in setting 
the shooting regulations, only a part of the 
season's young will have hatched. The 
production survey, therefore, consists of a 
measure of the number of broods on the 
water at the time of the survey plus a 
measure of weather, water, and other 
conditions that affect or reflect production 
success following the survey period. 
The bulk of the important waterfowl 
breeding areas in Alaska, Canada, North 
Dakota, South Dakota, and Minnesota are 
surveyed from the air. Statistically designed 
sampling techniques and similar methods of 
collecting and analyzing data are used 
throughout these areas. In addition to the 
areas mentioned, approximately 22 of the 
Northern States conduct breeding-ground 
surveys. Methods vary somewhat among 
these States, although in States with im- 
portant numbers of breeding ducks the 
methods are similar in most respects to 
those employed in the Dakotas, Canada, and 
Alaska. 
In recent years, aerial crews have 
sampled approximately 2,375,000 square 
miles of the best duck breeding habitat on 
the North American Continent. The only 
important duck breeding areas that are not 
being censused currently are those in 
eastern Ontario, Quebec, and Labrador, 
for which adequate census techniques have 
not yet been developed. 
The aerial crews count the birds on 
somewhat less than 1 percent of the total 
breeding area. This is sufficient coverage 
to reduce sampling error to less than 20 
percent of the average population density in 
most survey areas, and to much less than 
20 percent when considering the breeding 
range as a whole. 
The results of the breeding-ground sur- 
veys are presented as indexes. When con- 
ducting aerial surveys of breeding birds 
or of broods, not all birds present are 
