Sharp-tailed Grouse - Habitat Assessment

Habitat Assessment

Research conducted pre-1950 on sharp-tailed grouse habitat assessment was done visually. Hamerstrom (1939) reported sparse vegetation was seldom selected for nesting due toa lack of adequate cover. Habitat generalizations were formed based on the number of individuals found at a given local. These assumptions were "if" more birds were present at one location and less at another, "then" the first must be the better habitat. Hamerstrom (1963) observed 119 of 207 (57%) grouse broods frequenting savannah style habitat. He concluded that the savannah style habitat was the habitat needed for best management. As the research on habitat for grouse species matured, so did the techniques used for assessment. Cover boards and Robel poles were developed to measure visual obstruction (VO) and create habitat indices. Cover boards were developed as early as 1938 by Wight (1938) to study white-tailed deer habitat. Wight’s (1938) cover board was 6 feet in height, marked and numbered every foot. Visible marks were counted to measure obstruction by plants. Kobriger (1965) developed a 4 x 4 foot board marked at 3 inch intervals with alternating white and black squares. He placed a camera in the center of the breeding ground at a height of 3 feet. He then placed the cover board 30 feet away taking photographs of the cover board. After compiling all the photographs, they were analyzed with a hand lens to assess the number of squares visible. This number gave him a vegetation index of cover classes. This method has recently has been modified by Limb et al. (2007). Instead of taking photographs 30 feet away like Kobriger (1965), Limb et al. (2007) took photographs of vegetation back dropped by a 1x1 meter cover board at a height of 1 meter, 4 meters away. These digital photographs were uploaded to Adobe Acrobat and digitized to the 1x1 meter backdrop (Limb et al. 2007). Robel et al. (1970) developed a pole to determine height based on correlated vegetation weight. The pole was duly named the Robel pole. Robel et al. (1970) found that VO measurements taken at a height of 1m and a distance of 4m from the pole gave a reliable index of the amount of vegetation production at a location. Hamerstrom et al. (1957) were quoted as saying "Height and density of grass were clearly more important to the prairie chickens than species composition" as reported by Robel et al. (1970). This was also believed to be true for the sharp-tailed grouse. These key aspects can now be assessed using the Robel pole, Nudds cover board, and Limb et al. digital photography method effectively and efficiently.