Evaluation of Bias in Roadside Point Count Surveys of Passerines in Shrubsteppe and Grassland Habitats in Southwestern Idaho

Abstract

Breeding passerine abundances in Great Basin shrubsteppe and grassland habitats were surveyed in southwestern Idaho by using 73 pairs of 200-m radius circular point counts. Points were placed along roads and paired with points 400 m away from roads but in similar habitat. Grassland species such as Horned Larks (Eremophila alpestris) and Western Meadowlarks (Sturnella neglecta) accounted for 65 percent and 21 percent of the total number of individuals counted in both habitat types. Typical shrubsteppe bird species such as Sage (Amphispiza belli) and Brewer's sparrows (Spizella breweri), and Sage Thrashers (Oreoscoptes montanus) were less common (11 percent of the total counted). Except for Western Meadowlarks (P < 0.05), all comparisons between the number of individuals of a species counted at points on- versus off-roads were statistically insignificant (P > 0.20). Meadowlarks were likely over-sampled along roads because of the presence of adjacent fences, which provide conspicuous song perches.

Parent Publication

• Monitoring bird populations by point counts

Citation

Rotenberry, John T.; Knick, Steven T. 1995. Evaluation of Bias in Roadside Point Count Surveys of Passerines in Shrubsteppe and Grassland Habitats in Southwestern Idaho. In: Ralph, C. John; Sauer, John R.; Droege, Sam, technical editors. 1995. Monitoring bird populations by point counts. Gen. Tech. Rep. PSW-GTR-149. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 99-102