The bees are storing honey that will sustain them through the bitter winter and be sold in a gift shop just blocks away.
"Already this season, one hive has produced 200 pounds of surplus honey, which is really a huge amount of honey," said beekeeper Michael Thompson after checking the hives one July morning. "The state average is 40 pounds of surplus honey per hive."
The Chicago bees' success could be due to the city's abundant and mostly pesticide-free flowers. Many bee experts believe city bees have a leg up on country bees these days because of a longer nectar flow, with people planting flowers that bloom from spring to fall, and organic gardening practices. Not to mention the urban residents who are building hives at a brisk pace.
Beekeeping is thriving in cities across the nation, driven by young hobbyists and green entrepreneurs. Honey from city hives makes its way into swanky restaurant kitchens and behind the bar, where it's mixed into cocktails or stars as an ingredient in honey wine.
Membership in beekeeping clubs is skewing younger and growing. The White House garden has beehives. The city of Chicago's hives — nine in all, on rooftops and other government property — are just part of the boom.
"I've seen hives set up on balconies and in very, very small backyards," said Russell Bates, a TV commercial director and co-founder of Backwards Beekeepers, a 3-year-old group that draws up to 100 mostly newcomers to its monthly meetings in Los Angeles.
The group is "backwards" because its members rely on natural, non-chemical beekeeping practices. All their hives are populated by local bees they've captured — or "rescued" as the group's members like to say — from places they're not wanted.
"We don't use mail-order bees," Bates said. "Local bees have adapted to this environment. They're the survivors."
City governments, won over by beekeepers' passion, are easing restrictions. In recent years, New York, Denver, Milwaukee and Santa Monica have made beekeeping legal. The Backwards Beekeepers group is working to legalize beekeeping in Los Angeles.
The mysterious disappearance of honeybees, first reported in 2006 by commercial beekeeping operators who lost 30 to 90 percent of their hives, led some state agriculture departments to encourage hobby beekeeping. The U.S. Department of Agriculture estimates about one-third of the nation's diet directly or indirectly benefits from honeybee pollination.
Researchers have yet to determine a cause for "colony collapse disorder," but they say likely culprits include pathogens, parasites, environmental strains and bee management practices that cause poor nutrition.
In Washington, a biology professor who is studying whether pollen richer in protein makes bees healthier plans to compare urban bees' protein intake with that of bees in the country.
"Pollen contains a lot of protein. The amount varies from plant species to plant species," said Hartmut Doebel, George Washington University researcher and beekeeper. "One idea is that bees that are healthy will fight off diseases better."
The university is partnering with the restaurant Founding Farmers a few blocks away. The restaurant recently put six beehives on the roof of an academic building, and Doebel and his students will study the bees, tracking their pollen sources and their health. The restaurant will use the surplus honey on its menu.
"We don't expect honey this year," said Valerie Zweig, Founding Farmers' honey director. "We hope for next summer. One of our signature dishes is corn bread with honey butter. We'll use it in that and maybe in marinades or maybe a cocktail. We may showcase it on its own in a little honey pot with some iced tea."
Greg Fischer of Wild Blossom Meadery and Winery in Chicago has about 40 beehives in the city and another 60 in more rural areas. His company turns the honey into mead, a fermented beverage that can be dry like Riesling or sweet like a dessert wine.
Fischer once worked with a company that trucked bees around the country to pollinate sunflowers in South Dakota, almonds in California and other crops in other states. He said city bees kept by hobbyists and smaller operators are healthier than bees used in commercial agriculture.
"You're putting them on a semi and throwing a net over them," Fischer said. "You're on the road three or four days. It kind of stresses them out."
For some city residents, beekeeping represents a return to the family farms of their childhoods. Chicago resident Carolyn Ioder started hives two years ago after growing vegetables and raising chickens. Her bees live in three hives in a community garden in a once-vacant lot near a fire station and elevated train tracks.
"My husband and I are first generation off the farm," Ioder said. "Some people just come by and shake our hands and say thank you because they're so curious and they've never seen it and their children have never seen animals or chickens or goats before."
Urban beekeepers may be biased, but they contend their honey tastes better than country honey since it takes on essences from plants the bees visit.
Thompson stuck a toothpick into a small jar of Chicago City Hall honey and tasted it. He described it as complex with nectar from a variety of mints from Lurie Garden in Millennium Park and linden trees in Grant Park. The honey's taste changed after Lurie Garden was installed in 2004, he said.
"I guess it tastes more complicated now," he said.