Effects of Captivity on Roosting Behavior in the Endangered Whooping Crane (Grus Americana)

Abstract

A primary source of mortality in the Eastern Migratory Population (EMP) of whooping cranes (Grus americana) is predation, which inhibits the establishment of a self-sustaining population as required by the species recovery plan. Previously, birds released from captive rearing programs have shown variation in roost habitat choice, with some birds’ choices putting them at an increased risk of predation and human-wildlife conflict. This study aimed to answer if whooping crane chicks preferentially use water versus dry areas during roosting periods while in human care, and the impact of rearing in captivity on roost site selection after release into the EMP. Trail camera imagery was collected during the 2023 and 2024 chick rearing seasons (May-October) at the International Crane Foundation to assess how often the chicks utilized water for roosting at night. In addition to water use, sleeping behaviors were observed. All whooping crane chicks were observed roosting in water during the study, with the highest proportion of observations of chicks in water around 0100. After the 2024 release, roost sites of the release cohort at Horicon Marsh (n = 4) and White River Marsh State Wildlife Area (n = 1) were selected from Platform Terminal Transmitter (PTT) GPS data for the first 10 days after release. These roosting locations were assessed for water and vegetation cover to evaluate roost habitat quality. The juveniles released at Horicon Marsh selected sites with 100percent water cover, with most sites having 0percent vegetation. The juvenile at White River Marsh first selected sites that had low water coverage with high vegetation cover, and eventually used sites that were a matrix of 100percent water and varying levels of vegetation cover. Thus, the data from this study suggest that whooping cranes reared in environments with ponds will behave as management would expect after release into the wild. The impacts of differences in logistics across rearing facilities as well as release locations on reintroduction success are still unknown.