
57 
failure was skunk predation which accounted for 42, or 27.5 percent of the 153 
nests; crow predation destroyed 26 nests, or 17.0 percent of the total (Table IV.). 
It must be mentioned that most of our nest search was confined to 
brushy patches of snowberry and rose, and thus, the various cover types were not 
examined in proportion to their acreage on the study area. Stubble fields, known 
to provide cover for many pintails were almost untouched. However, farming 
operations were at least two weeks behind schedule this spring, and it appears that 
stubble nesters were unusuallysuccessful in producing broods. 
Hatching 
Broods were aged and back-dated to approximate date of hatch by use 
of the method developed by Gollop and Marshall. These approximate hatching dates 
were grouped by weekly intervals, and the curves for total waterfowl, pintail, 
mallard, blue-winged teal, and shoveler plotted (Figure 4). The earliest hatchings, 
those of pintails and mallards, were during the week of May 15-21. The pintail 
hatching curve rose to an abrupt peak during May 29-June 4, and then quickly 
declined. Subsequent hatchings continued in small numbers until July 17-23 when 
the last broods appeared. Analysis of the pintail curve suggests a very good first 
hatch. Mallard hatchings attained two peaks, one between May 22-28, and the 
other about three weeks later between June 12-18; this curve suggests a rather 
weak first hatch followed by a fair subsequent attempt. The blue-winged teal curve 
indicated a good first hatch while only a fair hatch is indicated for first shoveler 
attempts. 
Broods 
Three complete brood counts were undertaken between June 4 and 
August 10 on the study area (Table V.). In order to reduce duplication to a minimum, 
the surveys were spaced about one month apart. Only the first census on June 4-6 
was made with the aid of a dog; the other two were ''beat-outs". Broods were 
assumed to be present for "broody", or feigning hens. All broods noted for the 
three counts were totalled and corrected for suspected duplications and potential 
later broods. Thus, total brood production on the Success Study Area was calculated 
at 226, or 23.8 per square mile. Comparison of the percent composition of broods 
with that of the breeding population suggests that pintails, blue-winged teals, and 
shovelers experienced a better hatch than the average for all species combined, 
while mallards had slightly below average hatch. 
Complete counts were obtained for 345 broods of 11 species; these are 
summarized in Table VI. by the age groupclassification devised by Gollop. Because 
of the small number of known complete Class III broods observed, we supplemented 
these with Class IIc data to obtain sufficient information for broods attaining, or 
nearly attaining flight size. Broods for all species combined decreased from an 
average of 7.41 young for Class la to 6.48 for Classes IIc and III combined. This 
is a loss of only .93 young per brood, or 12.5 percent mortality, from the la figure. 
