Partnership Study on Nesting Success of Eastern Migratory Whooping Cranes

Contacts: Joan Garland, Outreach Coordinator, 608-381-1262

Black flies may be responsible for a high number of Whooping Cranes abandoning their nests in the core reintroduction area in central Wisconsin.  To test this hypothesis, the Whooping Crane Eastern Partnership (WCEP), the coalition of public and private groups that is reintroducing Whooping Cranes to eastern North America, has been conducting a multi-year study to examine the causes of nest abandonment.

The specific goal of this study is to temporarily remove target species of black flies from the environment and examine Whooping Crane nest success as a result.  Other factors that may relate to reproductive success are also being examined, including predation, food availability, and age/nesting experience of the birds in the population.

In spring 2011 and 2012, WCEP biologists conducted a two-year black fly suppression treatment to evaluate the role that black flies play in Whooping Crane nest abandonments.   Two rivers near Necedah National Wildlife Refuge (NWR) that were known to have significant populations of breeding black flies were treated with Bacillus thuringiensis israelensis (Bti), a naturally occurring soil bacterium used as an alternative to chemical pesticides to control insects. Bti is the most common, environmentally safe way to reduce adult black fly numbers.

Follow-up assessments found that the treatments during the two-year study significantly reduced black fly numbers during the Whooping Crane nesting season (view our spring 2012 update on this research).  This spring, no Bti treatment was applied, allowing researchers to differentiate between the increasing experience of the nesting birds at Necedah NWR and the effect of black flies.

Researchers use traps baited with dry ice to monitor the abundance of black flies and other biting insects throughout the nesting area in central Wisconsin (the CO2 in the dry ice attracts the insects). Hillary Thompson, ICF Field Ecology Intern Manager, is shown hanging a bag of dry ice on a trap at Necedah NWR.

Twenty Whooping Crane pairs have initiated nests this spring so far.  Seventeen of those nests were abandoned during a four-day period, from May 4-7.  Nineteen eggs were collected from the abandoned nests. At the time of egg collection, dense clouds of black flies were observed at the nests.  Several of the collected eggs have been determined to be fertile and are currently being incubated at the International Crane Foundation. They will be used in Whooping Crane reintroduction efforts.

“This study is critical to guide future decisions for how to manage Whooping Cranes that currently nest within the area affected by black flies, as well as where else we can work to re-establish Whooping Cranes in Wisconsin and in the Upper Midwest,” said Jeb Barzen, Director of Field Ecology, International Crane Foundation.

Whooping Cranes were on the verge of extinction in the 1940s. Today, there are only about 600 birds in existence, approximately 445 of them in the wild. Aside from the 106 birds in the WCEP population, the only other migrating population of Whooping Cranes nests at Wood Buffalo National Park in northern Alberta, Canada and winters at Aransas NWR on the Texas Gulf Coast.  A non-migrating flock of approximately 20 birds lives year-round in the central Florida Kissimmee region, and an additional 28 non-migratory cranes live in southern Louisiana.

WCEP asks anyone who encounters a Whooping Crane in the wild to please give them the respect and distance they need. Do not approach birds on foot within 200 yards; remain in your vehicle; do not approach in a vehicle any closer than 100 yards.  Also, please remain concealed and do not speak loudly enough that the birds can hear you.  Finally, do not trespass on private property in an attempt to view or photograph whooping cranes.

Whooping Crane Eastern Partnership founding members are the International Crane Foundation, Operation Migration, Inc., Wisconsin Department of Natural Resources, U.S. Fish and Wildlife Service, the U.S. Geological Survey’s Patuxent Wildlife Research Center and National Wildlife Health Center, the National Fish and Wildlife Foundation, the Natural Resources Foundation of Wisconsin, and the International Whooping Crane Recovery Team.

Many other flyway states, provinces, private individuals and conservation groups have joined forces with and support WCEP by donating resources, funding and personnel. More than 60 percent of the project’s budget comes from private sources in the form of grants, public donations and corporate sponsors.

Follow ICF’s Whooping Crane updates on Facebook and learn more about ICF’s commitment to the endangered Whooping Crane.


Crane Chick Cam

Hatching in May 2013! Tune in to ICF’s live Crane Chick Cam to view our Whooping Crane chicks as they are raised for reintroduction.


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