Authorities said they were called to the pond about 7 a.m. Saturday after a witness saw Hensley in his kayak being circled by a swan and then saw him go into and under the water.
Paramedics were unable to find Hensley, prompting dive crews to join the search and scour the 50-foot-deep pond, said Tony Brzezniak, deputy area commander for the Cook County sheriff's police. They located Hensley about 7:50 a.m., and he was taken to Advocate Lutheran General Hospital in Park Ridge, where he was pronounced dead about 8:15 a.m.
Using swans to chase away geese is an effective practice, experts said, because swans are larger and territorial and will live in non-native landscapes. They're also not afraid to compete with other animals for resources.
Swans, like many creatures, will defend their territory vigorously, especially when their young are involved, said Steve Sullivan, senior curator of urban ecology for the Chicago Academy of Sciences and its Peggy Notebaert Nature Museum.
"Swans are certainly perfectly happy to attack something that's much larger than them," Sullivan said. "It's mama with her babies, and mama with her babies is always ferocious."
Though swans may seem serene and are pretty to look at, most people don't realize how strong and aggressive they can be, said Doug Stotz, a senior conservation ecologist with the Field Museum. He said he has heard tales of people being attacked or injured from swans but has never heard of someone dying after a bad encounter.
Experts also said swans can be particularly nasty during the nesting and breeding season, which begins in early spring and goes through the summer.
Their first defense mechanism is to use their powerful wings to defend themselves or their offspring against predators, said Tim Snyder, curator of birds and reptiles at Brookfield Zoo.
Residents at Bay Colony Drive said the swans seemed to do their job. Resident Monika Woznica, 31, said Hensley had been a fixture at the pond for years, often bringing his kayak and sometimes his dog when he fed the swans and cared for them.
The area had been littered with geese droppings until Hensley came with the white birds, she said.
"After he started, (the area) became so nice," she said. "He was so good at what he did, very professional."
Authorities said Hensley's employer told them that it's mandatory for all employees to wear a life vest. Police said a life vest was found inside the kayak, though it wasn't immediately clear if that was a spare.
