Estimating sustainable mortality limits for shorebirds using the Western Atlantic Flyway

Of the 35 shorebird populations using the Western Atlantic Flyway for which trend data are available, more than 65% are experiencing declines. Due to their low reproductive potential, many shorebirds are vulnerable to perturbations in adult survival rates, and contemporary hunting pressure is emerging as a potential population-level constraint for some species. A central question is how much mortality these populations are capable of sustaining while maintainingpopulation sizes sufficient to meet biological and social needs. We used estimates of population parameters within a harvest-theoretic framework to estimate sustainable mortality limits for shorebird populations using the flyway (N = 37). Such limits varied over five orders of magnitude among populations, from less than 70 to more than 490,000 individuals and from 1 to 20% of the population estimate. Sustainable mortality limits were sensitive to adult survival and age at first reproduction. These relationships reflect the underlying slow-fast continuum in life-history strategies and suggest that species with long generation times and high adult survival are most vulnerable to elevated mortality rates. Shorebird hunting continues to be legal within many jurisdictions throughout the flyway, but flyway-wide harvest is virtually unknown for any species. Fragmentary information suggests that current harvest levels could contribute to observed declines for some species. Assessment of potential harvest impacts would be greatly enhanced by further defining those shorebird populations that actually use the flyway, improving confidence in demographic parameter estimates, and coordinating a flyway-wide estimate of harvest levels.