Whooping Crane Chick Survival in the Reintroduced Eastern Migratory Population

Abstract

The reintroduced Eastern Migratory Population (EMP) of Whooping Cranes (Grus americana) has exhibited appropriate breeding behavior, including pair formation, territory defense, nest building, and fertile egg production. However, recruitment has been lower than what is needed for a self-sustaining population due to high chick mortality. During 2006–2023, 194 chicks hatched in the EMP, with only 36 surviving to fledging. For the population to succeed without continued releases of captive-reared individuals, we must develop management strategies that increase recruitment to a level above mortality rates. We examined apparent weekly survival data of wild-hatched Whooping Crane chicks collected via aerial and ground surveys using radio telemetry from 2006 to 2023. In this study, we explored relationships between chick survival and a host of potentially impactful predictor variables including parental experience, parental life history, habitat, ecoregion, weather, and climate, as well as nest and clutch characteristics using Cox Proportional Hazard Regression Models. Our results indicate that a chick without a sibling has an increased probability of survival. Survival probability also increased with collective parental experience and warm days (> 32°C) during the first 4 weeks after hatch. Our data indicate that parental experience is a reliable predictor of recruitment. Adult survival may therefore be indirectly linked with low chick survival as experienced adults are too often lost from this population. Additionally, our results suggest that efforts to collect a single egg from two-egg nests may improve weekly survival of Whooping Crane chicks.