Steve Demkowski is a honeybee addict. But in January, when a swarm buzzed into his San José yard, the longtime beekeeper was stunned. Swarming had started nearly a month earlier than he expected.
“I wasn’t ready for it,” the 79-year-old said. “I have never gotten swarms in January before.”
Swarms happen when a bee colony splits, and half of it leaves to find a new home. It’s a natural process that usually ramps up in spring, when flowers are in bloom en masse.
Two more swarms that month would take up residence in his wrap-around yard, which is full of flowers, trees and bait hives smeared with lemongrass oil.
Demkowski isn’t alone in his surprise. A new report published by Swarmed, a resource for bee removal and a tracking network of more than 10,000 beekeepers, found that this year’s swarm season began an average of 17 days earlier than last year nationwide. In Bay Area counties, including San Francisco, San Mateo and Marin, some swarms arrived more than a month ahead of schedule. But bee experts think Swarmed’s four-year dataset needs additional time to establish a trend.
“The change was most pronounced in California, where warmer winter temperatures meant that the bees may have never gone dormant for the winter,” said Swarmed’s managing director, Mateo Kaiser, a fifth-generation beekeeper based in Mountain View.
Back at Demkowski’s residence, swarms kept arriving through February, until a cold snap slowed the South Bay buzz. He has kept bees for 35 years and said the warmer winter may have prompted the early swarms.
“I got more swarms than I have ever had,” Demkowski said. “But then it just stopped. Winter came back for a while, and it just messed everything up.”
This winter was historically warm across the Bay Area, with many areas shattering daily and monthly high-temperature records. Much of the West experienced the warmest winter on record “by a ridiculous margin,” said Daniel Swain, a climate scientist with UC Agriculture and Natural Resources.
Early swarming worries beekeepers because they can lose part of their colonies, which they rely on for pollination and honey production.
“If the winter is warmer, then maybe years of gut intuition are no longer serving you as well as they used to because it’s just harder to predict on your own,” Kaiser said. “Beekeepers are losing swarms that way and are worried about the health of their colonies later in the season.”
Kaiser also said he’s nervous that warmer winters could help varroa mites reproduce longer. The mites feed on bees’ fat reserves and can transmit deadly viral infections.
“If there’s less of a break happening and the bees are laying more eggs early in the winter, then the season for these mites to reproduce is also longer, and the colonies will suffer more because the mite loads are higher,” Kaiser said.
Demkowski fed his colonies a sugary syrup during the cold slump, determined not to lose any bees.
“They would’ve made it if we didn’t have almost two weeks of cold,” Demkowski said. “Because we have winter flowers like rosemary blooming about that time.”
With swarming in San Francisco County starting 78 days earlier than usual, Swarmed’s data showed that the city had the Bay Area’s biggest shift this year.
But Kaiser said the finding is “worth treating with a bit of caution” because the county’s distinct microclimates and weather patterns differ from the rest of the Bay Area, and fewer observations were collected across the county.
The smaller sample size could be due to the work of local swarm catchers, said Alex Unger, a board member of the San Francisco Beekeepers Association. The team fields hundreds of calls every year. The group verified its first swarm on Feb. 1, and then a second later that month. But then it was “pretty quiet” until May.
“Our first swarm was slightly earlier than what we might call the typical swarm season,” Unger said. “The bulk of our swarms have been slightly later than usual.”
Weather fluctuations from warm and sunny to cold and wet conditions could be part of why swarming slowed, Unger said, because bees love to forage on days warmer than 55 degrees. Unger said swarming suggests favorable foraging conditions and that bees are “doing really well.”
“It is definitely a signal of a warming planet, but early swarming bees is not in itself a crisis,” Unger said.
Scientists said the findings are compelling, but need more data.
Elina Niño, a University of California extension specialist in bees, has concerns about the report because many factors contribute to swarming, including human error, overcrowding, weather and regional ecosystem differences.
“I don’t know that early swarming is necessarily totally crazy, and we have seen it before on occasion,” Niño said. “Swarms really depend on the local climate.”
Niño said she would have more confidence once Swarmed has collected data for at least a decade. A longer record is especially important for understanding climate change, particularly in California, which has a broad range of ecosystems and natural swings from drought to deluge.
“I think this will be really super useful down the road,” Niño said. “It just needs a little bit more time before we start drawing extreme conclusions.”
James Nieh, a UC San Diego professor who studies animal behavior and specializes in social bees, has multiple apiaries and didn’t see unusual swarm activity this winter.
“It may have been in these other areas that they just had more access to food because of warmer weather earlier on,” Nieh said.
Nieh said more study is necessary to understand if the effects of human-caused climate change are behind a potential trend of early-season swarms. He is unaware of any peer-reviewed articles showing a long-term trend of honey bees in the U.S. swarming earlier due to climate change.
“Earlier swarming is consistent with what we know about climate-driven shifts in biological timing,” Nieh said, “but the specific connection between climate change and honey bee swarm timing still needs more direct study.”
Kaiser said his goal is to eventually offer the data as open source, so researchers and citizen scientists can further analyze the findings.
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