What is the temperature? You might have a beehive in your wall or attic. During winter bees stay warm inside of the hive, but they do take cleansing flight near the hive and many do die before returning back to the hive.
In January, a cold kill seems most likely explanation. Leaving hive to take poops sometimes leads to interesting consequences. "Cagey bees" story for another time.
maybe 10 or 12 months ago our next door neighbor had a swarm outside of her 2nd story. She came over for help - and I suggested calling vector control. They told her don't worry about it the queen is just probably taking a rest and may fly off once rested. They did. Other than that, no Bees until yesterday. Temp's at night have been in the mid upper 40s ..... & low 70s high 60s in the daytime. There doesn't seem to be any place along the house that they could have egress & that's the first thing I looked for. EDIT just looked out the slider now that it's almost 8:30 p.m. and, after hosing off all the bee Corpses, nice & clean concrete, there back again. 100's more. Looks like maybe 10% are still alive, mortally wounded, trying to fly but can't. Creepy, almost looks apocalyptic .
Well, at those temperatures bees are still active and not likely to die from cold. I am not exactly sure how honey bees behave in temperate regions like yours. If there are any flowers still blooming that they can forage, then they may be actively foraging all winter long and keeping the brood in a summer mode. OTOH, even though the temperature is warm enough for bees to come out of the hive, if there are no flowers blooming, then they would have to make it through the season with their stored honey in their hive. If they are short on storage, then they will come out of the hive but not finding any nectar source, the colony may die off. But the fact bees are out and about, and dropping on your deck, they may be sick from disease or starvation or mites. I still think there must be a colony somewhere close. Honey bees will happily live inside of wall or attic not visible from outside as long as there is enough space for them to get in and out. Only 1/4 inch opening is needed for them to pass through.
Can you google for any local bee keepers? They will often rush to help if they are close. At least they do here.
when the neighbor was inundated several months ago, she called the closest keeper (~3 or 4 miles away) & they weren't interested. 46° this AM (brrrr); got up on the 2nd story roof, crack of dawn. found the teeny hole they stagger out of, up high next to a dormer. nothing flowering now, or since last summer - so we'll figure it's the starvation / disease theory thanks for the thoughts !! .
Another starvation source could be an inexperienced beekeeper not providing enough food after collecting the honey. FLIRs and thermal cameras are used to see the extent of the hive, They can be huge.
Bees flight muscles don't function well at temperatures below 50°F. At 46°F, they can't fly far from the hive. That means yes, you do have a colony very close. At 40°F, they die. If it's windy or wet, they die quicker. Wintering bees stay in the hive and make a cluster and keep the core temperature above 80°F by sivering wings to generate heat. This activity takes energy source, so if they don't have enough wintering storage of honey, they can't survive. In my backyard apiary, I lose an average of ~30% hives over winter. But our winter is much harsher than yours. This morning's low was 9°F. Our daytime high in Jan usually does not get above 32°F. Catching swarming honeybees are much easier than removing an established colony inside of your wall. I can catch a swarm by setting up a trap, but trying to remove a colony inside of the wall is far more involved. You might want to give a call to the state agriculture dept who usually have an apiarist in charge or Beekeeper's association, they can give you who may be able to help you removing bee colony. The photo below is one of my hives that did not survive winter.
