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Providing evidence to improve practice

Individual study: Winter release of migratory whooping cranes Grus americana appears successful in wetlands in Florida, USA

Published source details

Urbanek R.P., Fondow L.E.A., Zimorski S.E., Wellington M.A. & Nipper M.A. (2010) Winter Release and Management of Reintroduced Migratory Whooping Cranes Grus Americana. Bird Conservation International, 20, 43-54


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Release captive-bred individuals into the wild to restore or augment wild populations of cranes Bird Conservation

A replicated study of a whooping crane Grus americana reintroduction programme in 2001-5 in wetlands in Florida, USA (Urbanek et al. 2010), found that winter-releases of this migratory bird proved effective. Average first-year survival of 71 winter-released juvenile birds was 87%, and was higher in later years as techniques improved. Birds were reared by humans wearing costumes (to avoid imprinting on human carers, see ‘Use puppets to increase the survival or growth of hand-reared chicks’ for studies on this intervention) and guided to the release site by an ultralight aircraft. Once there they were kept in holding pens by costumed caretakers. When the habitat prevented this, the juveniles were vulnerable to bobcat Lynx rufus predation, but this problem was overcome by vegetation clearance. Winter releases of this type were advantageous because the intensive care reduced predation by bobcats, juveniles were kept away from harassment by adult birds and juveniles did not lose their fear of humans through contact with tame sandhill cranes G. canadensis. Once released, juveniles showed ordinary migratory and summer behaviour.