Comparison of 3 surveys for estimating forest grouse population trends

Abstract

ABSTRACTBiologists in Oregon, USA, have routinely collected information on forest grouse populations over a 31‐year period (1981–2011) by 3 methods; however, it is unknown how well these methods detected variation in forest grouse abundance over time. We compared brood surveys, collection of hunter‐harvested grouse parts (wings and tails), and hunter‐harvest surveys to determine which annual survey was most useful as an index to forest grouse population trends in northeastern Oregon. All 3 surveys tracked both dusky (Dendragapus obscurus) and ruffed grouse (Bonasa umbellus) through 2 peaks in abundance separated by 14 years; however, stochastic variation resulting from small sample sizes reduced annual correlations among the methods. Grouse wing and tail collection was more informative than the other 2 indices because it exhibited the least annual variation, as well as provided estimates of both reproductive success and population size. Usefulness of hunter surveys was limited by funding, quality control, and lack of information on reproductive success. Brood surveys were the least useful of these indices because of inadequate sample sizes, particularly for ruffed grouse. The primary advantage of the brood survey was that it was available prior to the hunting season and could potentially help forecast the number of grouse available for the autumn hunting season. We recommend that grouse wing collections be continued, that consistency of hunter surveys be emphasized, and that sample size of brood surveys be increased to provide more reliable data. © 2015 The Wildlife Society.