Alternative methods for estimating density in an upland game bird: the red grouse Lagopus lagopus scoticus
Sharon A. Evans, François Mougeot, Steve M. Redpath & Fiona Leckie
Evans, S.A., Mougeot, F., Redpath, S.M. & Leckie, F. 2007: Alternative methods for estimating density in an upland game bird: the red grouse Lagopus lagopus scoticus. - Wildl. Biol. 13: 130-139.
For some species or habitats, 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-km² areas for 1-3 years in 2002-2004 using trained dogs and compared these density estimates (range: 23-220 grouse/km2) 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-km2 area. For dropping counts, we counted the number of fibrous dropping roost piles along two 1-km transects across each 1-km2 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.
Key words: count, density estimate, dropping transect, game bird, Lagopus lagopus scoticus, playback, red grouse, territorial bird
Sharon A. Evans, Steve M. Redpath & Fiona Leckie, Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK - e-mail: email@example.com (Sharon A. Evans); firstname.lastname@example.org (Steve M. Redpath); email@example.com (Fiona Leckie)
François Mougeot*, Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK, and Instituto de Investigación en Recursos Cinegéticos (IREC, CSIC-UCLM-JCCM), Ronda de Toledo, s/n, E-13005 Ciudad Real, Spain - e-mail: firstname.lastname@example.org
*Present address: School of Biological Sciences, University of Aberdeen, Zoology Building, Aberdeen AB24 2TZ, UK
Corresponding author: François Mougeot
Received 12 October 2004, accepted 27 March 2006
Associate Editor: Ilse Storch