
Breeding Ground Surveys 
Aerial 
Most of the low density areas included in past surveys were deleted 
and more intensive coverage was concentrated on the better breeding prounds in 
1955. A total of 3,088 linear miles of transect (772 square miles} were flown in 
1954, but only 2, 368 linear miles (460 square miles) in 1955. Conversely, the 
sampling intensity for all units of those strata censused in 1954 averaged 0,2 
percent, and for the more restricted coverage this year the sampling intensity was 
increased to 0.8 percent. 
Two types of transects were flown. Some of the areas were covered 
with the standard 16-mile transect using two observers, eachcounting a strip 
one-eighth mile wide on either side of the aircraft, Other areas were censused with 
one observer recording a strip one-eighth mile wide only, using a dictaphone. Two 
observers censused four square miles on each transect, whereas the one observer 
using a dictaphone censused only two square miles per transect. 
The dictaphone can be a great asset in recording observations from 
the air, but mechanical failure, unless detected immediately, can nullify the entire 
effort. Two such failures with different machines during the Alaska survey prompts 
the following recommendation to those using dictaphones in aircraft or automobiles. 
The power inverting unit for transforming 12 volt DC into 110 volt AC should be 
no less than 100 watt capacity. After considerable use a smaller inverter may 
still cut a dictabelt on the revolving drum without sufficient power to record audio 
as well. 
Table 1 summarizes the breeding pair survey. The population index 
from all areas comparable with the 1954 census indicates a decrease of considerable 
extent in the Ft. Yukon and Minto Lake areas, possibly 50 percent in the former and 
as much as 80 to 90 percent in the latter. Substantial pains elsewhere, however, 
partially offset these losses so that the over-all decrease was only 10 to 20 percent. 
It is of considerable interest that various phases of the Ft. Yukon 
study corroborate each other in indicating quantitiatively the lower production, 
The concurrent aerial and ground censuses of breeding pairs in June showed a 
reduction from the 1954 population of 29 percent on the ground and 45 percent in 
the aerial count. A reduction in broods of 51 percent was directly reflected in 60 
percent fewer ducks banded on the same area as last year with a comparable 
expenditure of time and effort. 
The population index of 350,000 as shown in Table 1 is not directly 
comparable with the 1954 population index of 798,000. The figure from last year 
includes over 227,000 square miles of low density habitat in which no transects 
were flown in 1955. In past aerial surveys these extensive low density areas have 
averaged slightly more than one pair of ducks per square mile. During adverse 
conditions elsewhere, e.g. Minto Lake in 1955, it is conceivable that much of this 
contiguous habitat will absorb birds forced from other areas. 
