LINE-TRANSECT SAMPLING FOR ESTIMATING PTARMIGAN (LAGOPUS SPP) DENSITY

Citation
L. Pelletier et Cj. Krebs, LINE-TRANSECT SAMPLING FOR ESTIMATING PTARMIGAN (LAGOPUS SPP) DENSITY, Canadian journal of zoology, 75(8), 1997, pp. 1185-1192
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
Journal title
ISSN journal
0008-4301
Volume
75
Issue
8
Year of publication
1997
Pages
1185 - 1192
Database
ISI
SICI code
0008-4301(1997)75:8<1185:LSFEP(>2.0.ZU;2-Q
Abstract
Current methods of estimating ptarmigan density require total counts, and hardly apply to areas exceeding 1 km(2). We evaluated the applicab ility, accuracy, and efficiency of line-transect sampling as an altern ative method for estimating breeding density of male ptarmigan. We com pared Hayne's and generalized Hayne's estimators with line transect es timators based on perpendicular distance. We surveyed 6 subalpine area s in Kluane, Yukon, with 231 km of transects in 1995 and 1996, in addi tion to a 77-ha grid where we also conducted total counts. Estimates o f perpendicular distance were accurate (bias = -3 to -7%). Their effic iency resides mainly in detecting changes in density over 2-year perio ds in highly or moderately fluctuating populations. Performance of Hay ne's estimator was close to that of perpendicular distance (coefficien t of correlation, r = 0.95), even if in many cases the average sightin g angle was not 32.7 degrees. The generalized Hayne's estimator was no t robust; biases were up to -90%. The results of this survey, with den sities ranging between 0 and 65 males/km(2) for similar and adjoining subalpine areas, dispute the principle that the ''health'' of a popula tion can be assessed by censusing only a small area.