Line Transect Method of Estimating Grouse Population Densities

SUMMARY A new estimator is proposed for estimating ruffed grouse population densities by the line transect method of sampling. The estimator, utilizing only the right angle distances from the observer to the sighted animal, is shown to be approximately unbiased and an approximate variance of the estimator is provided in explicit form. Both the estimator and its variance are dependent on specified assumptions. The expected length of line transect necessary to sample exactly n' animals is derived and, in 2-stage sampling, the additional miles of transect necessary to achieve a predetermined precision. The authors examine data for the years 1950-58 taken at Cloquet, Minnesota, on the ruffed grouse (Bonasa umbellus) and compare densities calculated from the new estimator with the estimated densities of the previously published Hayne, King, and Webb estimators for the line transect method. The underlying assumptions are discussed and several are tested on these as well as more extensive data.