Conservation In Action
Captive flocks of whooping cranes are maintained at Patuxent Wildlife Research Center in Maryland, the International Crane Foundation in Baraboo, Wis., the Calgary Zoo, the San Antonio Zoo and the Audubon Center for Research of Endangered Species at the Audubon Species Survival Center in New Orleans, La.
Wild whooping cranes usually lay two eggs, also called a “clutch,” in a breeding season, however will usually only raise a single chick. Whooping cranes that support the reintroduction project also usually lay two eggs, however, after the pair lays the second egg, the clutch is removed from the nest, which causes the cranes to lay again in about 10 days. By removing the eggs from the nest, the whooping crane pairs are three to four times more productive than wild whooping cranes in a breeding season.
Once an egg is laid, and is determined to be fertile and healthy, it is given to a sandhill crane pair for ten days. Each egg is given an identification number based on the parent's pen location and the order in which the egg was laid.
Sandhills are readily and easily available and are large enough to incubate two whooping crane eggs. A rating system is employed to determine the best pair of sandhills to incubate an egg. A sandhill pair will incubate and raise sandhill crane eggs for at least two years. After they show they are good parents, then they will be given a whooping crane egg. Each pair can serve as surrogate parents for around 15 years.
The surrogate sandhills will incubate the whooper egg for 10 days, with the male and the female alternating care of the egg. After 10 days, the egg will be removed from its surrogate parents, weighed and examined for fertility, and then placed in an artificial incubator.
Weighing the egg is crucial, as excessive weight loss indicates dehydration. Although fertile eggs do lose weight as the chick grows inside, too much weight loss can be fatal. To offset excessive weight loss, staff will increase the incubator’s humidity level. At 20 days, it is safe to place the egg in a mechanical incubator for the last 10 days of incubation.
Just hours before an egg hatches, movement can be detected and peeping sounds can be heard from the egg. For chicks that will be used on the ultralight-led migration, the handlers begin to play sounds of the ultralight aircraft engine to begin the imprinting process.
Chapter on Chick Rearing (PDF)
Marianne Wellington, Anne Burke Jane M. Nicolich, and Kathleen O'Malley. Citation: David H. Ellis, George F. Gee, and Claire M. Mirande, editors. 1996 Cranes: their biology, husbandry and conservation. U.S. Department of the Interior, National Biological Service, Washington, DC and International Crane Foundation, Baraboo, Wisconsin. 1996. xii, 308 p.
Protocol for Conditioning Costume-reared Whooping Cranes to Follow an Ultralight Aircraft in Migration
Training Techniques Slideshow
Cranes learn the migration route from the previous generation. Chicks hatched on the nesting grounds learn to fly with their parents, following them in the fall to the wintering grounds. Their destinations and the route they use may have evolved for thousands of years but it exists only in the memories of the birds that use it. If all individuals of a species are lost from a region, the route is lost forever. Birds that are raised in captivity lack an older generation to teach them and they tend to become resident, staying the entire year in the same location.
In 2001, Operation Migration’s pilots led the first whooping crane chicks, conditioned to follow their ultralight aircraft surrogates, south from Necedah NWR to Chassahowitzka NWR in Florida. Each subsequent year, WCEP biologists and pilots have conditioned and guided additional groups of juvenile cranes to Florida. Having been shown the way once, the young birds initiate their return migration in the spring, and in subsequent years, continue to migrate on their own. In 2008, St. Marks NWR along Florida’s Gulf Coast was added as an additional wintering site for the juvenile cranes.
The use of ultralight aircraft is effective because of the bird's natural instinct to imprint. Once hatched, the chick is attracted to the first creature that nurtures it, normally the parent. This is nature's way of ensuring the offspring stays close and is protected by the adults. The procedure we follow replaces the parent bird with the handler and so the birds imprint on the surrogate parent. Prior to hatching, a recording of the aircraft engine is played to the chicks. They are introduced to the ultralight at about seven days of age and they soon associate it with the handler. The birds are not trained to follow the aircraft; instead they are conditioned to it as an extension of the handler. After they arrive on the wintering grounds and reach the sub-adult stage, they become independent (much like human teenage offspring) and they no longer look to the handler and aircraft for security and comfort. Unlike training, the conditioning diminishes with maturity.
To see the status of the ultralight migration visit the Operation Migration Field Journal. Opportunities to see the ultralight migration along the migration route will be posted in the journal.
Direct Autumn Release: a Second Technique for Reintroducing Young cranes
Direct autumn release is a reintroduction technique that is used in addition to the primary ultralight aircraft-led technique. The direct autumn release technique used in the eastern migratory whooping crane reintroduction consists of rearing whooping crane chicks according to a strict costume/isolation-rearing protocol and then releasing them with older whooping cranes that have successfully migrated in the past or into wild sandhill flocks with which these older whooping cranes are likely to associate. Chicks for direct autumn release are reared from an early age in the field and then released after fledging. These released juveniles then learn a fall migration route from the older, wild birds. This method of reintroduction has been extensively tested and proven previously successful with sandhill cranes.
The direct autumn release of whooping crane chicks complements the success of the ultralight-led migrations conducted by the Whooping Crane Eastern Partnership (WCEP). The DAR technique affords several key benefits: (1) pending availability of eggs, a larger number of whooping cranes can be reintroduced into the migratory pathway each year, and (2) this technique could be used to continue adding birds to the population if the ultralight-led portion of the project ever became unavailable. In addition, the few chicks originally designated for ultralight-led migration but later found unsuitable can be salvaged by releasing them in the fall according to similar methods used in the direct autumn release. Otherwise, these latter birds might be placed into captivity and lost from the population.
Questions and Answers about the Direct Autumn Release method.
Management and protection of the whooping cranes on their Florida wintering grounds takes a dedicated team of WCEP members from the International Crane Foundation, Operation Migration and the U.S. Fish and Wildlife Service.
Once the birds arrive at their wintering locations, they are placed into top-netted pens until health checks are completed. For the remainder of the winter, they are free to fly in and out of a larger pen. During the day, the birds oftentimes explore outside of the enclosure, foraging for food and exploring their surroundings, but for safety, return to roost on the man-made oyster bar inside the pen at night.
In the evening, the winter management team uses a loud Whooping crane voice recording to call the birds back into the pen. Usually the roost check takes around two hours.
The winter management team is also responsible for bringing out fresh water and food to be stored and dispensed from barrels.
Duff and other WCEP partners that work one-on-one with the birds must wear a costume that prevents the cranes from getting attached to people.
In early winter, the birds are checked on twice a day to check water levels, food, and observe the birds’ behavior, and to ensure they are all inside the pen at roost time.
After the chicks were released from the pen WCEP winter management teams would walk them to the oyster bar every evening to teach them where to roost.
In late winter, the birds are checked once a day at roost time. As spring approaches, the team also monitors behavior that may indicate the birds are ready to start migrating northward.
WCEP winter management crew with the International Crane Foundation and U.S. Fish and Wildlife Service are also part of the WCEP tracking team, which is responsible for monitoring all of the migratory whooping cranes currently wintering in Florida that were part of previous ultralight and Direct Autumn Release migrations. Often times the tracking team must coordinate with landowners for access to their property to monitor the birds. Some previously released cranes winter in other states outside of Florida, including Alabama, Georgia, Tennessee, and South Carolina, so trackers often travel long distances during the winter to track the birds. The tracking team also processes public sightings of wintering migratory whoopers. To submit a report of your sighting, visit http://www.fws.gov/midwest/whoopingcrane/sightings/sightingform.cfm.
Spring and Summer Monitoring
Spring and summer monitoring protocols are dependent on events and available resources. The top priority is monitoring nesting activity which is done by the Wisconsin DNR, International Crane Foundation, Fish and Wildlife Service staff. During the spring and summer of 2012 Lighthawk provided pilots for nesting monitoring flights. The goal was to fly daily morning and afternoon flights - but weather prevented flights on many days.
LightHawk is a volunteer-based environmental aviation organization that provides donated flights to support conservation projects.
The next priority is monitoring the movements and success of the 1-year old birds, both Direct Autumn Release and ultralight-led cranes.
Along the way, we try to record all birds when encountered, which includes cooperators like the state DNRs, but also an increasing amount of general sightings information comes from the reporting web site. We have also used dataloggers at various locations, but are getting more serious about that, and in the process of setting up dataloggers at Horicon National Wildlife Refuge and White River State Wildlife Management Area. The dataloggers scan for signals and record when birds pass within range of the antenna. With some limitations, it gives us an ability to record a birds presence in a general area, with little effort.