Atypical primary molt patterns in greater sage-grouse: implications for age classification

Brett L Walker,Michael A Schroeder

doi:10.2981/wlb.00855

Abstract

Age-specific patterns of primary molt facilitate age classification of native North American upland gamebirds, a critical step in understanding their ecology, behavior, life history, population dynamics and harvest. However, deviations from typical molt patterns can create confusing plumages that complicate age classification. We examined data from live-captured greater sage-grouse Centrocercus urophasianus across seven studies in five U.S. states and wings from harvested birds in Oregon and Colorado for evidence of atypical primary molt. We documented atypical replacement through primary nine during preformative molt, atypical retention of juvenile primary 10 during second prebasic molt, and atypical retention of basic outer primaries during definitive prebasic molt. Atypical primary molts were observed more often in live-captured females (3.2%, n = 561) than males (0.8%, n = 494). Many individuals with atypical primary patterns, especially females, are difficult or impossible to reliably age by plumage or morphology and may bias research and harvest data.

Highlights

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We identified two atypical males that had retained juvenile P10 during second prebasic molt
The inability to differentiate atypical HY or SY females that replaced through P9 during preformative molt from atypical SY or TY females that retained juvenile P10 during second prebasic molt reveals some of the complexities of age classification caused by atypical molt

Summary

Introduction

BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Age-specific patterns of primary molt facilitate age classification of native North American upland gamebirds, a critical step in understanding their ecology, behavior, life history, population dynamics and harvest. We examined data from live-captured greater sage-grouse Centrocercus urophasianus across seven studies in five U.S states and wings from harvested birds in Oregon and Colorado for evidence of atypical primary molt. Accurate age classification is essential for understanding gamebird life histories and population dynamics (Bergerud and Gratson 1988), generating age-specific vital rate estimates from marked bird populations (Connelly et al 2011), modeling population demography and viability (Johnson and Braun 1999, Taylor et al 2012, McCaffery and Lukacs 2016) and estimating productivity from harvest data (Hagen and Loughin 2008, Hansen et al 2012, Braun et al 2015). The license permits use, distribution and reproduction in any medium, provided the original work is properly cited

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