Greater Prairie Chicken Appears On Comeback Trail In Illinois
CHAMPAIGN, Ill. - Booming mating calls rocked the Illinois prairie in the mid-1800s, announcing that colorful greater prairie chickens were near and abundant. As pioneers moved west, the birds were hunted for food. They fell to predators, their habitats shrank, and, scientists say, even the birds' declining genetic diversity brought their near extinction.
In the Friday (Nov. 27) issue of the journal Science, nine researchers report that an isolated group of the birds is making a comeback. The potential recovery is the result of an experimental conservation-management program, in which birds from other states were added. The program was based on genetic findings and 35 years of population monitoring.
The greater prairie chicken (Tympanuchus cupido pinnatus) is estimated to have numbered in the millions in Illinois when pioneers moved west. They were "shot by the wagonload for food," said Ronald Westemeier, a recently retired scientist with the Illinois Natural History Survey and lead author of the Science article. As the prairie diminished, so did the birds' habitat - from more than 60 percent of the state to less than 0.01 percent and in just two isolated populations in Jasper and Marion counties. From 1962 to 1994, in Jasper County alone, their numbers fell from 2,000 to less than 50.
Among those 50, Westemeier said, only six were resident males, which are known for the colorful orange sacks that inflate on each side of their necks during their mating call. According to this year's count, not covered in the study, males number 84 in the Prairie Ridge State Natural Area in Jasper County in southeastern Illinois, where Westemeier had directed the comprehensive greater prairie-chicken monitoring program since 1966.
"Right now, it looks very good," Westemeier said. "I feel like I am going out on a high note. Rather than seeing this population of Illinois birds lost altogether, we are seeing a recovery. I am very glad to see this."
The findings of the paper, Westemeier said, indicate "the need for grassland habitat and for sufficiently large populations," and it raises a bigger question of just what makes a viable population to assure a species' survival. Co-author Jeffrey D. Brawn agrees: "Viability is really the key word," he said. "This is how we gauge how self-sustaining a population is. If it is viable, it means it is producing enough young to persist.
"We're cautiously hopeful that they are making a comeback," said Brawn, a scientist with the Illinois Natural History Survey and an affiliate of the University of Illinois department of ecology, ethology and evolution. "The message of this paper is that fragmentation and habitat loss can really lead to a number of problems in conserving species. In this case, these factors led to genetic problems. What was interesting is that the people who manage the population did their best, going to extraordinary measures to preserve this population over the years, yet it kept going down and down, owing to the fact that it was just a small relic population that had low genetic diversity.
"What we did by bringing in the other birds for genetic management is a classic case that importation of birds from healthy populations elsewhere can work," Brawn said. "It may not work every time. We were able to base the effort on an immense amount of information collected by Ron Westemeier. Mixing stocks depends a lot on the adaptations of different populations elsewhere. If we had brought in prairie chickens from Texas, which had adapted to the hot climate there, we may not have had the same success."
The success - in which more than 500 birds were brought in beginning in 1992 from larger populations in Minnesota, Kansas and Nebraska - could serve as a model to save dwindling populations of wild species from extinction, the researchers say. The 35 years of data represent one of the most detailed sets of data ever collected from an isolated and declining wildlife population.
The research began in 1963 and involved the work of 29 teams of two to 15 researchers and field assistants from numerous jurisdictions. Each year researchers methodically documented yearly changes in prairie-chicken numbers and nesting success.
The nine authors of the paper, in addition to Westemeier and Brawn, were Scott A. Simpson and Terry L. Esker of the Illinois Department of Natural Resources, Newton; Roger W. Jansen of the Douglas-Hart Nature Center, Mattoon; Jeffrey W. Walk and Eric L. Kershner , U. of I. department of natural resources and environmental sciences; and Juan L. Bouzat and Ken N. Paige, U. of I. department of ecology, ethology and evolution. Simpson and Esker directed the transfer of non-resident birds into Illinois.
As part of the project, Paige and Bouzat determined by genetic analysis, including that of museum specimens from the 1930s, that the isolated Illinois birds had been part of a much larger population, and they concluded that a lack of genetic diversity resulted from population decline. Specifically, they found that 95 to 100 percent of the alleles - alternative genes that provide the codes for particular characteristics - present in the Illinois birds also were in the birds in other states, and that the other populations contained additional alleles that provide for greater fitness. Somewhere in time, perhaps in the 1970s, the Illinois birds lost about one-third of that diversity in their genetic makeup.
The Paige-Bouzat findings, Brawn said, possibly explained a decline in hatching rates of eggs, from a 93 percent success rate in the 1930 to just 38 percent by 1990. By 1996, with the importation of birds, fertility had risen and the hatching rate rose to 94 percent. "We don't have absolute smoking-gun evidence, but this is an unusually strong case where everything seems to corroborate it," he said.
Researchers also had documented that no major environmental or climatic events could have accounted for the increased hatching rates in recent years.
"These genetic findings are important, because no other studies have been able to show precisely what was lost, leaving alternative possible interpretations such as they were always depauperate [lacking] in genetic variation. These alleles are merely markers of overall genetic diversity and the alleles lost over time. But it can be implied that a loss in genetic variation was a factor because the introduction of new genetic material by these outside birds bolstered fitness back to original levels," Paige said.
Greater prairie chickens once occupied the prairies from Canada to Texas. They are considered virtually extinct in Canada; their southern cousin, the Attwater prairie chicken, is endangered on the Texas coastal prairie. An eastern relative, the Heath Hen, has been extinct since 1931. The current range of the greater prairie chicken is from northwestern Minnesota south to northeastern Oklahoma, and from southeastern Illinois to northeastern Colorado.
Efforts to save the Illinois population must continue, the researchers say. "Illinois is the prairie state; 60 percent was once prairie," Westemeier said. "We've lost all that. I guess it's a matter of atonement that we owe something to the prairie chicken. This bird probably numbered in the millions in the 1800s. It fed the early settlers. The species epitomizes the characteristics of the state. Besides, efforts to preserve prairie chickens benefit a wide array of other endangered, threatened and watch-list species in the state."
The prairie chickens' recovery, Brawn said, may be temporary, and it may be necessary to bring in more birds in several years to revitalize the population's diversity. A good sign, he added, is that the Illinois Department of Natural Resources has been protecting and developing grasslands to expand the Prairie Ridge park.
"I think the prognosis is guardedly optimistic," Brawn said. "This is one of the few populations of prairie chickens east of the Mississippi River. Every time we let a population go, or allow a regional extinction, it's just one more ratchet on biodiversity. We lose something. I think Illinois has a real vested interest in this. I think it would be a real loss in our identity, in our heritage, if we didn't have wild prairie chickens in our state."
Funding sources varied widely in the 35 years of work. In their study, the researchers recognized the Illinois Department of Natural Resources, the Federal Aid Wildlife Restoration Project, U.S. Fish and Wildlife Service, Illinois Natural History Survey, The Nature Conservancy, Illinois Nature Preserves Commission, Illinois Endangered Species Protection Board, University of Illinois, Illinois Wildlife Preservation Fund, Natural Areas Acquisition Fund, and the Illinois Council on Food and Agricultural Research.