Temporal covariation of lesser scaup demographic rates
The continental population of scaup (
Aythya affinis and
A. marila) fell to >30% below the 1955-2008 average, and ~3 million birds below the North American Waterfowl Management Plan (NAWMP) goal of 6.3 million. Reviews of long-term databases noted a decrease in the sex and age ratios (number of females relative to males and number of immatures relative to adults, respectively) of lesser scaup in the U.S. harvest. These results indicate that recruitment and female survival of lesser scaup has declined during this period. Recruitment is the product of several demographic rates, including female survival during the breeding season, breeding propensity, nesting success, and duckling survival. Previous life-cycle models were unable to investigate the response of population growth rate to correlations between demographic rates because the models were developed from multiple studies and areas. The Red Rocks Lake National Wildlife Refuge in southwestern Montana provides a unique opportunity to collect the full range of demographic rates on breeding lesser scaup, which will allow us to construct a population model for lesser scaup that will incorporate covaration in demographic rates. Objectives of the study are 1) concurrently estimate key demographic rates for lesser scaup from a single population (seasonal survival of females, breeding area fidelity, breeding propensity, nesting success, duckling survival, and first-year survival of females); 2) evaluate the relative contribution of habitat and climate factors in variation and covariation of demographic rates; and 3) conduct a prospective perturbation analysis for lesser scaup that incorporates covariation in key demographic rates. The study has collected extensive data on scaup demographic rates and environmental factors starting in 2006, and full demographic data since 2011. Field work and analyes are ongoing.