Harold F. Mayfield, 95, an acclaimed ornithologist whose research unlocked the secrets of the rare Kirtland's warbler, and a personnel executive at Owens-Illinois Inc. who used his work experience to come up with a method to calculate species' nesting success, died yesterday in the Swan Creek Retirement Village.
He had been in declining health for about seven months.
Formerly of Waterville, Mr. Mayfield lived at the retirement village for several years.
He retired at 60 from O-I to spend more time on ornithology, the scientific study of birds.
"I've been an example of what an amateur can do," Mr. Mayfield told The Blade in 2002 after he was chosen to receive the Robert Ridgway Award from the American Birding Association for a lifetime of publications in field ornithology.
Still, his amateur status was a formality. He published more than 200 scholarly papers.
He was, at various times, president of the American Ornithologists' Union, the Wilson Ornithological Society, and the Cooper Ornithological Society - the only person to have led ornithology's three major organizations.
His 1960 monograph about the Kirtland's warbler was considered central to solving the mysteries of the endangered species, which until recent years nested only in a narrow section of northern Lower Michigan. It winters only in the Bahamas.
The species only nests in sandy soil beneath stands of jack pine trees young enough to still have lower branches close to the ground. That means the birds depend for their survival on periodic forest fires that clear old-growth trees and allow the regrowth of jack pines to provide ground cover.
Mr. Mayfield found that the brown-headed cowbird, which lays its eggs in other species' nests, could be especially devastating to the Kirtland's warbler population.
His research led to aggressive trapping of the cowbirds in the Kirtland's range. He helped develop a federal-state-private Kirtland's warbler recovery plan in 1974.
The species, at its low point several decades ago, had 167 males. There are more than 1,400 now.
According to the Michigan Department of Natural Resources, all nests until 1996 were found within 60 miles of one site. Since then, a small number of nests have been found each year in the Upper Peninsula, and the species has nested in Wisconsin and Ontario.
"That's quite remarkable," said Elliot Tramer, a University of Toledo professor of ecology and a longtime friend. "No one has played a larger role than Harold in the recovery of the Kirtland's warbler from extinction."
Mr. Mayfield's monograph was deemed "the most important recent work on the birds in the Western Hemisphere" by the American Ornithologists' Union, which in 1961 gave him its top honor, the Brewster Memorial Award, for his work.
"That study pretty much set the standard for life history studies of birds. It was so thorough and well done," Mr. Tramer said.
Mr. Mayfield long had an interest in the polar regions. He was widely known for his research into the red phalarope, a seabird that nests on the Arctic shore for only a few weeks annually, spending the rest of its life in the world's oceans.
In the bird study world, Mr. Mayfield was most known for his "Mayfield Method," used to calculate a species' nesting success. Mr. Mayfield, who had a master's degree in mathematics, said that the method was an outgrowth of his professional work at O-I in calculating workplace safety records.
"Without formal training in ornithology - he was essentially self-taught - he was able to make these remarkable contributions," Mr. Tramer said.
Mr. Mayfield received many awards, among them the Arthur A. Allen Award of the Cornell Laboratory of Ornithology in 1990 and a Lifetime Achievement Award from the Toledo Naturalists' Association in 2003.
Born in Minneapolis, he was adopted as an infant and grew up in Burlington, Iowa, and Alton, Ill., where he attended high school.
He received a bachelor's degree from Shurtleff College, now part of Southern Illinois University, and a master's degree from the University of Illinois at Urbana/Champaign.
He taught high school a short time before he was hired in 1935 by what is now O-I at its plant in Alton.
He was athletic into adulthood, playing tennis and semi-professional basketball until a stroke at 28. He was partially paralyzed for a time and walked with a limp for several months.
He took stock afterward and began bird watching to relax. As his interest grew, he visited the University of Michigan and became friends with the curator of birds there. The curator had begun a study of the Kirtland's warbler; Mr. Mayfield continued the work after the curator's death.
Mr. Mayfield was also respected in personnel management and was the author of more than 90 papers on workplace matters. His work appeared in the Harvard Business Review.
For his accomplishments in business and biology, he received honorary doctorates from Bowling Green State University and Occidental College in California.
Surviving are his wife, Virginia, whom he married in 1936; sons, John and Charles Mayfield; daughters, Sigrid Boie and Sheryl "Mindy" Mayfield; four grandchildren, and two great-grandchildren.
Arrangements are pending at the Coyle Funeral Home.
The family suggests tributes to Toledo Area Metroparks.