The Validity of the Roadside Census as Applied to Pheasants

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Abstract
Past experience in various states and the present study in Montana show that great variation exists in the results of roadside cen-susing of pheasants. A statistical study of the data set forth by other workers and of individual censuses, bi-weekly and monthly averages of censuses in Montana shows the results to be highly erratic and not in line with known seasonal changes in total population. Further, various anomalous sex ratios appear to complicate the results. Varying weather conditions have an effect on the number of birds seen: more birds are found on days with dewfall than on dewless days; clearness or cloudiness of the weather has little effect; and birds are more in evidence on rainy or snowy days than on freezing days. A positive correlation was found between amt. of dewfall and number of birds observed, and a correction factor was computed, but the prediction index shows that < 10% of the variability of the censuses can be attributed to variations in dewfall. Tests made to determine the time of appearance after sunrise of most of the birds demonstrated no constancy, but the first half-hr. after sunrise is the most variable. Our data together with that of others demonstrate that the results of the roadside census for pheasants are too variable for reliable conclusions. The factors responsible for this high coeff. of variation are complex and difficult of measurement. Although no satisfactory method of censusing pheasants quickly and accurately has yet been devised, it seems apparent that methods other than the roadside census promise more accurate and dependable results.

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