Northern Prairie Wildlife Research Center
Avian Census Methods
I censused breeding bird populations during 2-30 June 1982 using a modified Emlen line transect (Emlen 1971, 1977). Each of the 30 draws was visited three times during this count period. Count times were from local sunrise to 1100. During each count, data were recorded on the location of each male bird of a species encountered (except that for brown-headed cowbirds only females were counted). These locations were marked on field maps and used for later analyses. Each census plot except one was 50 x 400 m in size, covering an area of 2.0 ha. The other census plot was 1.7 ha. The centerline and adjacent edges of each plot were marked with colored plastic surveyor's tape.
In addition to census plots, occasional investigations of habitats adjacent to the wooded draws were made throughout the study area. These data were used to supplement observations made in each area, and to provide further information on the numbers and kinds of birds occupying wooded draws and adjacent habitats.
The method used for this investigation was a modification of the James and Shugart (1970) circular plot method described by Noon (1981). Vegetation within each draw was sampled in five 0.04-ha circular plots. This allowed me to analyze the vegetation on 0.2 ha of each bird census plot. Vegetation within the draws was sampled beginning at the top of the draw, and then proceeding downslope. Vegetation sample plots were at 0, 50, 150, 250, and 350 m along the bird census transect.
Click on the to view the corresponding data for that census point or follow the links listed below.
-- Results and Discussion