- Author: Kathy Keatley Garvey
Back in July 2023, we wrote a Bug Squad blog about a feral bee colony inside a cavity of a sycamore tree on the UC Davis campus.
The triple-digit temperatures resulted in bee bearding.
Bees engage in bearding (forming a "beard" outside their hive or colony) when the temperature soars and it's too hot to maintain the internal 94 degree temperature. As the late Extension apiculturist Eric Mussen (1944-2022) of the UC Davis Department of Entomology and Nematology used to say: All honey bee colonies must maintain a temperature of 94 degrees, or the brood (eggs, larvae and pupae), will be adversely impacted. When the inside temperature rises above 94 Fahrenheit, bees resort to (1) bringing more water into the colony to cool it down and (2) bee bearding, meaning that some of the adults will leave the colony and "beard" just outside the entrance to help reduce the heat load inside. The "bearders" are helping their brothers and sisters-to-be survive.
Today the sycamore tree colony is expanding. With binoculars or a telephoto lens, you can clearly see the comb build-up.
It's a beautiful, incredible sight--Mother Nature at her finest--and something we never tire of seeing. Seeing a wild bee colony is bee-lieving.
![Close-up of a feral bee colony living a sycamore tree on the UC Davis campus. Image taken Sunday, Sept. 3, 2023. (Photo by Kathy Keatley Garvey) Close-up of a feral bee colony living a sycamore tree on the UC Davis campus. Image taken Sunday, Sept. 3, 2023. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/101717.jpg)
![A wide-angle view of the feral bee colony that is living in a sycamore tree cavity on the UC Davis campus. Image taken Sept. 3, 2023. (Photo by Kathy Keatley Garvey) A wide-angle view of the feral bee colony that is living in a sycamore tree cavity on the UC Davis campus. Image taken Sept. 3, 2023. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/101718.jpg)
![This was the hot-weather scene in July 2023 when bees bearded outside their home in a sycamore tree on the UC Davis campus. (Photo by Kathy Keatley Garvey) This was the hot-weather scene in July 2023 when bees bearded outside their home in a sycamore tree on the UC Davis campus. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/101719.jpg)
- Author: Kathy Keatley Garvey
Have you read the excessive heat warnings and the guidelines to prevent heat illnesses as triple-digit temperatures hold us hostage in Yolo and Solano counties and elsewhere?.
UC Davis Safety Services related this week:
- Know the signs and symptoms of heat exhaustion and heat stroke.
- Keep potable water on hand at all times for consumption. It is recommended to ingest approximately four 8-ounce cups of fresh water per hour
- Cool off in well shaded or air-conditioned areas.
- Wear lightweight, loose-fitting and light-colored clothing.
- If possible, stay indoors and avoid strenuous work during the hottest part of the day.
- Minimize direct exposure to the sun whenever possible and wear sunscreen to prevent sunburn.
- Never leave children, disabled adults, or pets in parked vehicles.
- Listen to local weather forecasts and stay aware of upcoming temperature changes.
But what about the feral honey bee colonies?
All honey bee colonies must maintain a temperature of 94 degrees, or the brood (eggs, larvae and pupae), will be adversely impacted, as the late Extension apiculturist Eric Mussen (1944-2022) of the UC Davis Department of Entomology and Nematology used to say. When the inside temperature rises above 94 Fahrenheit, bees resort to (1) bringing more water into the colony to cool it down and (2) bee bearding, meaning that some of the adults will leave the colony and "beard" just outside the entrance to help reduce the heat load inside. The "bearders" are helping their brothers and sisters-to-be survive.
That said, it was interesting this week to see the bee-bearding phenomenon on a feral honey bee colony in a sycamore tree on the UC Davis campus. Most people and bicyclists wouldn't notice it, unless they're inclined to look up 30 feet.
Bees know what they're doing,. and they've been bearding for millions of years. So, no poking, no prodding, no choking them with smoke, no dousing them with water. Or worse, what if a passerby panics and calls an exterminator?
Just leave 'em alone. The bees know what they're doing.
They're engaging in thermoregulation. When the temperature drops below 94, they'll cluster and shiver their wing muscles to keep the colony warm. If the temperature rises above the required temperature, the worker bees will gather more water and deposit the droplets inside the hive so other bees can fan and cool the colony. Bearding is part of the process.
As Mussen told us: "Like most other animals, the bodies of honey bees are mostly water. Thus, they need to drink water routinely as we do. Additionally, water (or sometimes nectar) is critical for diluting the gelatinous food secreted from the head glands of nurse bees, so that the queen, developing larvae, drones, and worker bees can swallow the food. They use water to keep the brood nest area at the proper relative humidity, especially when it gets hot and dry outside the hive. Water droplets, placed within the brood nest area, are evaporated by fanning worker bees and that cools (air conditions) the brood nest area to keep the eggs and developing brood at the critical 94 degrees Fahrenheit required for proper development."
"On extremely dry, hot days, all bee foraging except for water will cease," Mussen noted. "Under those conditions it has been estimated that the bees may be bringing back nearly a gallon of water a day."
We could learn a thing or two from the bees.
(See the bee activity on this UC Davis campus 'bee tree' on a YouTube video)
![As temperatures soar, feral honey bees engage in bearding to reduce the heat load inside. These bees are in a sycamore tree on the UC Davis campus. (Photo by Kathy Keatley Garvey) As temperatures soar, feral honey bees engage in bearding to reduce the heat load inside. These bees are in a sycamore tree on the UC Davis campus. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/100766.jpg)
![Honey bees buzz in and out of their colony inside a sycamore tree on the UC Davis campus. Bee bearding helps reduce the heat load inside. Honey bee colonies require a temperature of 94 degrees for the developing brood. (Photo by Kathy Keatley Garvey) Honey bees buzz in and out of their colony inside a sycamore tree on the UC Davis campus. Bee bearding helps reduce the heat load inside. Honey bee colonies require a temperature of 94 degrees for the developing brood. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/100770.jpg)
- Author: Kathy Keatley Garvey
Call it “The Battle Over a Tree Hollow."
Feral bees have occupied—and abandoned—a sycamore tree cavity in a Vacaville neighborhood for at least two decades. They occupy it in the spring, summer and fall, and then the colony either absconds or dies back in the winter.
When this winter proved exceptionally cold and rainy, a clever squirrel moved in.
A place to stay warm. A perfect sleepy hollow.
Then in early April, scout bees from a spring swarm begin circling the tree. Wait! There's an intruder inside.
Squirrel: "Occupied! No vacancy!"
Bees: "Out, it's ours!”
Squirrel: “Finders, keepers! I was here first!”
Bees: “But it's ours! This is our bee tree!”
Cars speed by. Residents trudge by with leashed dogs. Birds chirp. A hound bays uproariously. The sleepy squirrel pokes his head out occasionally as if to ask “What's all the ruckus about? Can't a squirrel get some sleep?”
More bees buzz around his head.
“Occupied!” Mr. Squirrel shouts again. “No vacancy!”
The score: Squirrel: 1. Bees: 0.
Then one mid-April day, the tenant vanishes.
The bees quickly move in. Call it a "hollow victory" for the bees.
The score: Bees: 1. Squirrel, O.
Now a queen bee is busily laying eggs. The workers are performing their age-related duties: nurse maids, nannies, royal attendants, builders, architects, foragers, dancers, honey tenders, pollen packers, propolis or "glue" specialists, air conditioning and heating technicians, undertakers, and guards.
Who was it who said "Everything works if you let it?" The American rock band, Cheap Trick.
So true.
![Look closely and you can see a squirrel occupying a small hollow or cavity in a sycamore tree. The cavity has been home to feral bees for at least two decades. (Image taken in Vacaville by Kathy Keatley Garvey) Look closely and you can see a squirrel occupying a small hollow or cavity in a sycamore tree. The cavity has been home to feral bees for at least two decades. (Image taken in Vacaville by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/99061.jpg)
![What's all that noise about? Can't a squirrel get some sleep? (Photo by Kathy Keatley Garvey) What's all that noise about? Can't a squirrel get some sleep? (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/99062.jpg)
![The squirrel pokes his head out of his home, his sleepy hollow. (Photo by Kathy Keatley Garvey) The squirrel pokes his head out of his home, his sleepy hollow. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/99063.jpg)
![Occupied! No vacancy! The squirrel is aware that bees are circling, trying to move into Occupied! No vacancy! The squirrel is aware that bees are circling, trying to move into](/blogs/blogcore/blogfiles/99064.jpg)
![With the squirrel gone, honey bees quickly move into the hollow. (Photo by Kathy Keatley Garvey) With the squirrel gone, honey bees quickly move into the hollow. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/99065.jpg)
Help and Advice from the Help Desk of the Master Gardeners of Contra Costa
Client's Request for Information and Advice:
The tree has received water from the lawn that surrounds it, although I am now cutting back to watering only every two weeks due to the drought, which I understand should be sufficient for the tree. It has not been pruned except occasionally to keep it out of the power lines. Large roots are visible on the surface of the lawn. I believe the only fertilizer it has received would have been when the lawn was fertilized, which hasn't occurred for probably ten years.
I hesitate to contact a tree pruner, as I am not confident that they would give me an accurate, unbiased answer since it would be in their interest to suggest that pruning was necessary.
MGCC's Help Desk Response:
Thank you for contacting the Master Gardener Help Desk.
You are right to be concerned about your tree, especially during the drought. Trees on residential properties can add value to the property, provide a pleasant setting for the house, neighborhood and community, shade from the hot summer sun, and a “sense of place”. There would no doubt be different neighborhoods without our trees. Because of these factors, homeowners taking good care of their trees are usually amply rewarded.
Your Sycamore tree is probably a California Sycamore (Platanus racemosa), a widely planted residential tree for its beauty and shade which can live for over 150 years. While generally easy to get along with, Sycamores do have their problems at times, namely Anthracnose and Powdery Mildew (see http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/sycamore.html). Overall though these are usually minor irritants to the homeowner if the tree is properly cared for, e.g. watering to maintain its health, and some pruning to provide for appropriate growth.
However, our research find that Sycamores are known to experience a phenomenon called "Summer Branch Drop". More information about this phenomenon can be found at this link from the Journal of Arboriculture. (http://bit.ly/1HormZb)
While Master Gardeners can provide advice and appropriate references on the care of your Sycamore, we are not professional arborists, especially for significant concerns such as yours. From the pictures of the overhanging branches, it would seem that an assessment of the health and well-being of your Sycamore by a professional arborist is appropriate. While the cost of professional consultation is not insubstantial, the payback in peace-of-mind and protection of your investment in the tree and house could be substantial. So, in spite of your misgivings about the motivations of a tree service company, we would strongly advise that you have your tree inspected and evaluated by a certified arborist, probably a consulting arborist to provide a neutral 3rd party evaluation. Certification of arborists is by the International Society of Arborists (ISA). Some certified arborists are independent consultants while others are associated with specific tree care companies. While the independent consultant's consultation is probably close to a given fee, you should be able to request an estimate from any tree maintenance company for their proposed work. UC provides some advice on dealing with contractors and consultants at this link (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74125.html).
ISA Certified Arborists in our area can be found at this link http://www.isa-arbor.com/findanarborist/findanarborist.aspx. Once on line at the ISA page, to find an arborist in our area, use the Search by location function. Choose United States from the pull down menu, then type in the zip code and radius of interest (25 miles should be more than ample) and search again. This will bring up a list of certified arborists who work in our area as well as distinguishing who that are associated with and/or an independent consultant. My search found that there are many certified arborists to choose from in our area.
It appears that the tree has been receiving reasonable cultural care. Fertilizing established trees is usually not necessary. Your watering schedule may be sufficient, but we recommend that you speak with the arborist about caring for your tree during the drought as well, especially since you have exposed roots.
I hope that this information is helpful. Please do not hesitate to contact us again if you need further assistance.
Help Desk of the Master Gardeners of Contra Costa
Note: The Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/