Sage Grouse Hatching Success and Chronology for South-Central Montana

Abstract

A recent short-term fluctuation in sage grouse (Centrocercus urophasianus) abundance for south-central Montana was attributed to dramatically reduced productivity. This period of low productivity was associated with a peak hatching date 2 weeks earlier than normal. Molt patterns for adult hens indicated the early hatch was due to a shift in breeding and nesting and not reduced survival during June. These molt patterns also indicated a significant attempt at renesting by hens ≥ 2 years of age during periods of low productivity. To test the influence of climatic conditions on hatching chronology, I selected years that were at least one standard deviation above or below the long-term average for hatches occurring before 1 June. I concluded that early hatches occurred during warm dry springs, which were also associated with drought conditions. Warm dry springs also may result in earlier dates for spring green-up and grasshopper hatches. I interpret early hatches as an adaptation by sage grouse hens to take the best possible advantage of cover and forage conditions during the first critical weeks of life for their chicks.