Whooping cranes (Grus americana) are one of the most rare, highly endangered and intensively monitored bird species in North America. The Aransas-Wood Buffalo population (AWBP), which breeds in northern Canada and winters in Texas, is the only remaining wild, self-sustaining migratory population of whooping cranes. Whooping cranes from the AWBP was reduced to a mere 15 individuals in 1941 and has rebounded to its peak population size of 329 in December of 2015. The ongoing recovery of this whooping crane population is perhaps one of the greatest endangered species success stories. The International Whooping Crane Recovery Team recommended the establishment of additional migratory and non-migratory populations to safeguard against extinction.
In addition to the AWB, other populations of whooping cranes exist in Wisconsin, Florida, and Louisiana due to the efforts of many government agencies and non-governmental organizations, including the captive breeding centers where whooping cranes are reared for reintroduction. By the end of 2015 there were approximately 145 birds in reintroduced populations and 161 birds held in captivity. The Florida and Louisiana populations are reintroduced non-migratory flocks; whereas, the eastern migratory population (EMP) of whooping cranes was established in 2000 with the goal of establishing a migratory, self-sustaining population in Eastern North America. This fits into the overall recovery strategy of working to establish one or more additional whooping crane flocks that are distinct from the AWBP as outlined in the International Whooping Crane Recovery plan.
Reintroducing Whooping Cranes
The Whooping Crane Eastern Partnership (WCEP) formed to restore a migratory population of whooping cranes to eastern North America. There are currently 111 whooping cranes in the Eastern migratory population (EMP) as a result of WCEP’s efforts, which began in 2001.
Founding members of the Whooping Crane Eastern Partnership (WCEP) are the International Crane Foundation, International Whooping Crane Recovery Team, Operation Migration Inc., National Fish and Wildlife Foundation, Natural Resources Foundation of Wisconsin, U.S. Fish and Wildlife Service, USGS/Patuxent Wildlife Research Center and National Wildlife Health Center, and Wisconsin Department of Natural Resources.
Many other flyway States, provinces, Native American tribes, private individuals and conservation groups have joined forces with and support WCEP by donating resources, funding and personnel.
Whooping cranes being released in this reintroduction project have come from captive whooping crane flocks in Maryland, Wisconsin, and Alberta. Eggs produced by captive cranes are hatched in incubators and chicks are then raised using two methods: Costume-reared and/or Parent-reared. There are strict protocols in place designed to prevent the chicks from imprinting on humans.
Cranes for the reintroduction also come from nests in Wisconsin, which may be abandoned due to swarms of Black flies pestering the nesting cranes. These eggs are collected and placed in temporary incubators until they can be delivered to the International Crane Foundation near Baraboo, Wisconsin. They may either stay at ICF to be hatched, or they may be sent on to additional captive breeding centers.
Training and Releasing Cranes
Beginning in 2001, the whooping crane chicks were transported to Wisconsin in June where they were conditioned to follow ultralight aircraft in preparation for their fall migration to wintering grounds in Florida. Pilots led the birds on training flights over the reintroduction area throughout the summer to build the birds’ stamina. Every year 2001 – 2015, a class of cranes was guided on their first migration south from Wisconsin to Florida’s Gulf Coast. This method helped to establish a core group of migratory cranes.
Beginning in 2005 the ultralight-led migration was supplemented with a second reintroduction technique called Direct Autumn Release (DAR). Young cranes were released in small groups with wild whooping cranes, with the intent that they will learn the migration route from these older, more experienced birds. After learning the migration route, the young cranes make the return flight to their summering grounds in the north on their own the following spring.
Beginning in 2016, cranes will not be led by ultralights on their first migration. Instead, all captive-bred chicks will be released with adult Whooping cranes that already know a migration route.
After several years of successful experimentation, beginning in 2016, a method called the Parent-reared release method is the main rearing and release method used. This method involves having captive parent cranes hatch and raise the youngsters with minimal contact with humans. When the birds are ready for release, they are transferred to Wisconsin where they are released into the company of free-ranging adult cranes that do not have their own wild-hatched young. The hopes are that the young birds will learn more natural “crane like” behaviors from the captive adults, ultimately making the offspring more attentive and when it comes time for them to begin breeding.
The goals of the reintroduction is to establish a migratory flock of the endangered birds, numbering 100, and includes 25 successfully breeding pairs. We’ve reached that first goal so now we are working to determine how best to help the cranes become better at raising young.
All birds are banded with a unique combination of color bands to allow for their identification in the field. Every bird is also outfitted with a VHF transmitter that allows biologists to track their locations with handheld receivers. Some of the cranes also carry satellite and cellular-based transmitters which allow us to locate them if they are lost or out of range of traditional receivers and to track them year round. WCEP project biologists track and monitor the released cranes in an effort to learn as much as possible about migration behaviors, habitat selection, and to monitor movements and survival. Results of monitoring are reported in the Project Updates.