COUNTING DEAD BIRDS - EXAMINATION OF METHODS

We studied three methods (line transect, circular quadrat, complete co unt) for estimating density of dead birds, using models of sparrows an d meadowlarks placed at a density of 50 birds of each type/ha. Line tr ansects with a 500-m search line were used in cultivated pasture and n ative prairie habitats. The number of birds found by individual search ers in line transects varied markedly, particularly, in pasture habita t. More birds were found, and birds were detected at a greater distanc e, in prairie than in pasture. More meadowlarks than sparrows were fou nd in both habitats but the mean estimated density of meadowlarks was greater than that of sparrows only in prairie. The number of birds fou nd during most searches was less than that suggested for estimating de nsity accurately and longer search lines were required. Density estima tes obtained using circular plots to sample 10% of the prairie area ra nged from 20 to 80 birds/ha for meadowlarks and from 10 to 60 birds/ha for sparrows in prairie habitat. A complete search by 25 volunteers s paced at 4 m intervals detected 90% of meadowlarks but only 62% of spa rrows in pasture habitat. Mean (SD) time for a single search, includin g searchers and recorders, was 3.0 (0.8), 1.5 (0.3), and 7.5 person-ho urs, for line transect, circular plot and complete search, respectivel y.