NEW YORK — Donal C. O’Brien, 79, who was the Rockefeller family’s lawyer for five decades but perhaps had his greatest impact as the longtime chairman of the National Audubon Society, died Sunday at his home in New Canaan, Conn.
The cause was pneumonia, his daughter Constance O’Brien Ashforth said.
Mr. O’Brien was a member of the National Audubon Society’s board for 25 years and its chairman for 15. He drove the organization’s efforts to identify thousands of “important bird areas’’ around the globe and to give people a global sense of the environment by highlighting the four flyways that take many species between the Southern Hemisphere and the North.
“Birds don’t know about state boundaries,’’ said David Yarnold, the chief executive. “Donal was always urging Audubon to think the way birds see the world — to think about large-scale conservation.’’
In 2010, the organization granted Mr. O’Brien its highest honor, the Audubon Medal. “He was passionate to the bone about birds,’’ Yarnold said.
Like many early conservationists, Mr. O’Brien expressed much of that passion through hunting; he also amassed an enormous collection of duck decoys and carved his own, twice winning national amateur competitions. His puffin carvings placed along the shoreline helped the Audubon Society to bring the Atlantic puffin back to the Maine coast after an absence of 100 years.
In a Sports Illustrated 1971 profile, he explained his love of heading out on frigid mornings to stand on an ice-slicked sea wall for good shooting.
“I like the whole thing,’’ he said, “feeling the cold, picking up the decoys, and when I am home on Sunday and think about what I did on Saturday, I’m revitalized and prepared to go back to the office.’’ The office was at the white-shoe firm of Milbank, Tweed, Hadley & McCloy, which he joined in 1959.
The next year he did some work on the estate of John D. Rockefeller Jr. He would go on to become chief counsel to the Rockefeller family. In that capacity, Mr. O’Brien set up the Rockefeller Trust Co. and became involved with leadership of organizations founded or supported by the family, including Rockefeller Center, the New York Blood Center, and the National Urban League. He retired from the firm in 2011.
Along with Audubon, Mr. O’Brien led the Atlantic Salmon Federation and such organizations as BirdLife International and the American Bird Conservancy. He served Connecticut as a 23-year member of its Council on Environmental Quality.
Donal Clare O’Brien Jr. was born in Manhattan. He graduated from Williams College and the University of Virginia law school. In 1956, he married Katharine Louise Slight. In addition to his wife and daughter Constance, Mr. O’Brien leaves a son, Donal C. O’Brien III; two other daughters, Katharine O’Brien Rohn and Caroline O’Brien Thomas; two brothers, Jonathan and Stephen; and 11 grandchildren. A third brother, C. David, died in 2011.
Robert Shaw, an expert on American folk art and a former curator at the Shelburne Museum in Vermont, said Mr. O’Brien’s love of hunting and preserving habitats went back to the roots of the American conservation movement.
“There was so much slaughter going on in the late 1800s and early 1900s’’ in commercial and sport hunting, Shaw said. “That’s where conservation started, to try to save birds.’’
Like Theodore Roosevelt, he said, Mr. O’Brien “was somebody who moved in the high tiers of society, but his play time was in the outdoors,’’ and he wanted to ensure that such experiences were available to future generations.