Chapter 21 - The Operation of an Aircraft-Led Migration: Goals, Successes, Challenges 2001 to 2015

Abstract

In order to enhance the prospect of survival for the Whooping Crane (Grus americana), the International Whooping Crane Recovery Team proposed establishing additional, discrete populations. Whooping Cranes learn migration behavior and a migratory route by following their parents. However, the Whooping Cranes that once used the eastern flyway were extirpated in the 1800s. Through a series of studies using nonendangered species, Operation Migration (a Canadian and U.S. nongovernment organization), developed a method of teaching nidifugous birds to migrate by conditioning them to follow modified ultralight aircraft. The success of those studies led to a plan to reintroduce migratory Whooping Crane into the eastern flyway. In 1998, the Whooping Crane Eastern Partnership, a consortium of nine federal, state and private agencies was established to manage the introduction of an Eastern Migratory Population. Each year from 2001 to 2015 captive-sourced eggs were hatched at the USGS Patuxent Wildlife Research Center in Maryland. Before they could fly, the Whooping Crane chicks were reared by costumed handlers and conditioned to follow the aircraft on the ground. Prior to fledging, the birds were relocated to Wisconsin and learned to fly there while following the ultralight aircraft. They were exercised daily with the aircraft, weather permitting and were socialized into a cohesive flock prior to the start of the migration. Over 15 years, 167 Whooping Cranes were trained to migrate and released using the aircraft-led release method. The migration covered 1669 km, crossed seven states from Wisconsin to Florida and took an average of 84.3 days to complete. On the wintering grounds, the birds were housed in an isolated, open-topped pen that encompassed 1.43 hectares. They were encouraged to fly out during the day to forage for natural foods and were called or led back into the pen in the evening where they could water-roost while protected from predators by the enclosure. All of the birds led south initiated northward migration in the spring on their own. Whooping Cranes reintroduced using this method displayed appropriate behavior: selected proper habitat, avoided humans, and paired with conspecifics. First year and annual survivorship was comparable to the extant Aransas/Wood Buffalo population (AWBP), however reproduction has thus far failed to reach a selfsustaining level. The cause of the low recruitment has yet to be determined.