Alternative methods for estimating density in an upland game bird: The red grouse Lagopus lagopus scotieus

For some species, reliable quantitative estimates of population size can be difficult to obtain. Density estimates of red grouse Lagopus lagopus scoticus are usually obtained through counts using trained pointer dogs. In this paper, we examine two alternative, and potentially easier, methods for estimating red grouse breeding density: one direct, based on counts of males responding to playbacks of territorial calls, and one indirect, based on counts of droppings along transects. We counted grouse on 14 1 -km(2) areas for 1-3 years in 2002-2004 using trained dogs and compared these density estimates (range: 23-220 grouse/km(2)) with density estimates derived from playback counts and dropping counts. For playback counts, we counted males responding to a playback of territorial calls at nine points spread over a given 1-km(2) area. For dropping counts, we counted the number of fibrous dropping roost piles along two 1-km transects across each 1-km(2) area. Generalised Linear Models indicated that male, female and total grouse density, measured by counts with dogs, could be predicted from playback counts of males, and that total grouse density could be predicted from dropping counts. However, playback counts provided better predictions than did dropping counts. Neither time of day nor wind affected responses to playback, but in clear weather fewer males responded than was expected. Playback counts could thus provide a useful alternative method for estimating grouse density, when or where counts with dogs are not feasible.