Winter Distribution Dynamics and Implications to a Reintroduced Population of Migratory Whooping Cranes

Abstract

From 2001 to 2012, the Whooping Crane Eastern Partnership released 196 costume-reared juvenile whooping cranes Grus americana in the eastern United States in an effort to reintroduce a migratory population of this endangered species. Techniques included leading juveniles from Wisconsin to wintering areas by ultralight aircraft or direct release of juveniles in Wisconsin prior to their first autumn migration. With few exceptions, ultralight-led cranes released on the Florida Gulf Coast wintered in inland freshwater habitats in subsequent winters. Wintering of the population occurred in four general regions: Florida–southern Georgia, coastal Carolina, the Mid-South (primarily Tennessee and northern Alabama), and the North (Indiana, Illinois, and Kentucky). Releases of ultralight-led juveniles resulted in the majority of the population returning to winter in Florida during the early years of the reintroduction. Later direct autumn releases and shortstopping by ultralight-led birds increased numbers in the Mid-South. Winter climate played a large role in wintering in the North. Drought resulted in changes in wintering locations, especially in Florida. Other factors influencing changes in distribution included habitat degradation and associations with other whooping cranes, especially new mates and birds released by different techniques. Breeding pairs and direct autumn-released birds exhibited greater winter site fidelity than did nonbreeders or ultralight aircraft-led birds, but fidelity was low for all groups. Causes of mortality differed across the winter range, with predation being most prevalent in Florida and gunshot accounting for the majority of mortalities north of Florida. Because most pairing occurred in central Wisconsin, the widespread winter distribution had no apparent negative effect on pair formation. There was no clear relationship between winter region and subsequent incubation success. The widespread distribution of the population poses minimal risk to the outcome of the reintroduction in comparison to reproduction problems in the core reintroduction area of central Wisconsin.

Experience drives innovation of new migration patterns of whooping cranes in response to global change

“…Whooping cranes migrate and overwinter in small but demographically heterogeneous groups 17 21 , providing opportunities for social learning via interactions between birds of different ages. During the study period, whooping cranes overwintered in groups ranging from 1 to 22 individuals (mean 3.62±s.d.…”

“…Migratory movements of all individuals in the population have been extensively monitored since the beginning of the reintroduction, resulting in a unique dataset where birds in the population have been tracked throughout their lifetimes. We use these long-term monitoring data of 175 individuals to investigate both the intrinsic and extrinsic drivers of shortstopping in the population 21 .…”

The importance of early life experience and animal cultures in reintroductions

“…For migration in particular, individuals from diverse bird species are known to be flexible in the spatial elements of their migration behavior (Gill et al., ; Vardanis, Klaassen, Strandberg, & Alerstam, ), meaning that animals have the potential to modify their migration patterns depending on environmental and social contexts. In this population of whooping cranes, shortstopping did not appear until years after reintroduction began (Teitelbaum et al., ; Urbanek et al., ), but the behavior emerged shortly after release of the first conspecific‐trained birds; it is unknown whether shortstopping would have emerged in aircraft‐trained birds if conspecific‐trained birds had never been released. Nevertheless, this rapid change in migration behavior illustrates the importance of animal cultures and social learning not only for maintaining behaviors across generations, but also for promoting rapid adaptation on the population level.…”

“…Migratory behavior in whooping cranes is culturally inherited in the wild, where juvenile whooping cranes spend up to 11 months with their parents (Johns, Goossen, Kuyt, & Craig‐Moore, ), but individuals continue to adapt their migration behavior into adulthood (Mueller, O'Hara, Converse, Urbanek, & Fagan, ; Teitelbaum et al., ). In the eastern migratory population, this adaptability has resulted in a dramatic northward shift in overwintering location in the 15 years since the beginning of its reintroduction; this shortstopping behavior has reduced the average migration distance of the population by about 50% (Teitelbaum et al., ; Urbanek, Szyszkoski, & Zimorski, ). Furthermore, within the reintroduced eastern migratory population, two different reintroduction methods have produced two distinct early migratory experiences: aircraft‐trained birds were initially taught to migrate by following an ultralight aircraft to their wintering grounds, whereas conspecific‐trained cranes follow other birds (usually other whooping cranes but occasionally sandhill cranes Antigone canadensis ), rather than an airplane, on their first southward migration.…”

Tamaño poblacional y patrón de conducta de Grus canadensis nesiotes (Aves: Gruidae) en dos localidades de Cuba

“…Respecto a 1998 hubo un ligero decremento que puede ser indicio de presiones por la pérdida del hábitat de alimentación asociado a la expansión de la planta exótica Dichrostachys cinerea en pastizales y sabanas naturales (Muñoz, Pereda, Ponce, Cruz, & Olazábal, 2009). La pérdida de hábitat conlleva al desplazamiento de individuos hacia zonas alejadas de la protección del área protegida Reserva Ecológica Los Indios y sus zonas aledañas (Urbanek, Szyszkoski, & Zimorski, 2014) donde pueden enfrentar amenazas como la cacería furtiva, que conduce rápidamente a un decline en poblaciones pequeñas. Este tema se debe considerar con intensidad para trazar estrategias de manejo de hábitat y conservación de la población.…”