478 Natural Resources Systems Copyright Goodheart-Willcox Co., Inc. Incomplete Counts Incomplete counts are counts are done in specifi ed areas, typically in quadrats, that use the average of specimens counted in multiple areas. For larger species, such as deer, a large crew is needed to drive the animals from one side of the quadrat so they may be counted by stationary members on the other three sides of the quadrat. There must be suffi cient drivers and observers for this method to be accurate. Booming ground counts, roadside counts, and strip censuses are also types of incom- plete counts. A booming ground is the area in which the male of certain grouse performs mating displays in which they make booming or drumming sounds with their wings. The counter deter- mines a transect line through the representative area and records the distances along the line at which the birds are located. A transect line is a line that is marked at regular intervals and used to divide an area, Figure 19-15. The transect line may be indicated with a rope or measuring tape, or determined visually with no actual markings. This pro- cess is repeated in multiple locations. The researcher would then determine the average of the combined counts. In a roadside count, a road is used as the transect line. Counts are made by observers from a slow-moving vehicle. A strip census is performed along a strip of land, such as the area along a road. Additional methods may be used to conduct a transect survey. Counts may be made of each species found below the knots on a rope or markings on the measuring tape, found directly under the entire length of the line, or within a specifi ed number of feet on either side of the line. Indirect Counts When performing an indirect count, the researcher uses indirect signs of the species’ presence and does not count the animals themselves. A scientist can determine the amount of scat, the number of constructed shelters, such as nests or burrows, damage to trees, marking or damage to the ground, and even listen for sounds of the animals to determine populations. When using indirect counts, the researcher must make assumptions about their estimation. If a researcher is counting scat, for example, he or she might assume that more scat in an area is a direct indication of more animals in the area when it may be the same animals defecating more in one area than another. Random, Systematic, and Stratifi ed Sampling Quadrats may be randomly selected, systematically arranged, or stratifi ed by some physical feature of the landscape, Figure 19-16. Random sampling is per- formed by randomly selecting and sampling small areas within the larger area. Systematic sampling involves sampling in a systematic way, such as on a grid sys- tem. The area is divided into even grids and then one sample is taken from each grid. Stratifi ed sampling is accomplished by taking samples of an area according Should the President be allowed to withdraw environmental policies that have helped reestablish endangered species populations? Explain why or why not. Thinking Critically Ivan Godal/Shutterstock.com Figure 19-15. The wood grouse or western capercaillie (Tetrao urogallus) is often counted during mating season. Researchers can use a transect line through the breeding area to obtain accurate numbers.