VALIDITY OF PRAIRIE GROUSE HARVEST-AGE RATIOS AS PRODUCTION INDICES

Abstract

The ratio of juveniles to adults in the fall harvest is a common index of production for Galliformes. The percentage of juvenile birds in the harvest has been shown to decline as the hunting season progressed for many galliforms, resulting in a biased index of production. Therefore, we used wing samples of plains sharp-tailed grouse (Tympanuchus phasianellus jamesi) and greater prairie-chickens (T. cupido pinnatus) from 4 public land areas in the Nebraska Sandhills, Nebraska, USA, to assess the potential for bias in harvest-age ratios across time. We hypothesized that the ratio of juveniles to adults in the harvest could change over time if susceptibility to harvest and/or fall survival were different between the juvenile and adult prairie grouse (Tympanuchus spp.) in the Nebraska populations. We found no change in the harvest-age ratio over time in either the sharp-tailed grouse or greater prairie-chicken data. Our findings were consistent with the published literature on harvest-age rates for sharp-tailed grouse but inconsistent with the greater prairie-chicken literature. Therefore, we maintain that analysis of the harvest data for bias due to a changing harvest-age ratio as the hunting season progresses is an essential adjunct to subsequent analysis or comparisons of production indices based on harvest-age ratios. In addition, limitations of harvest-age ratios must be known and care must be taken to minimize other potential biases before using harvest-age ratios as an index to production.