Black-rumped bumblebees swarming in bird house --- what do we do? - Ask Extension
After chickadees nested in a bird house on our back porch, we took it down a month ago to clean it and discovered a black-rumped bumblebee nest inside...
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Black-rumped bumblebees swarming in bird house --- what do we do? #923064
Asked December 23, 2025, 6:17 PM EST
After chickadees nested in a bird house on our back porch, we took it down a month ago to clean it and discovered a black-rumped bumblebee nest inside. Today, Dec. 23, they appear to be very active. Are they swarming? What will happen next? Any advice about how we can remove them from the back porch and from the bird house? We don't want to hurt the bees but we would like to get the bird house ready for the next round of chickadees to use it!
Lane County Oregon
Expert Response
Hi Nancy,
This is darn peculiar. I have a strong suspicion it is the Black-tailed Bumble Bee (Bombus melanopygus) which one of the few bumble bee species that like to nest in bird boxes:
https://www.inaturalist.org/taxa/130222-Bombus-melanopygus
Typically, these are the first bumble bee colonies to finish, with the nests collapsing by early summer. The typical life cycle is a single queen starts a new nest in January-February. This nest grows until the colony makes a new batch of queens and males and then the nest collapses. I typically get a lot of calls about this nest in May-June. So to find a nest in December is highly unusual.
To start, can you let me know where in the state are you located and if this bumble bee looks to be the one you are seeing?
If the nest is somehow hanging on from the summer (because we still have not had a cold snap) then I expect the nest will be ready to clean out for the chickadees. If it is just starting then the nest won't vacate until the spring. But get me some information and we can take it from there.
This is darn peculiar. I have a strong suspicion it is the Black-tailed Bumble Bee (Bombus melanopygus) which one of the few bumble bee species that like to nest in bird boxes:
https://www.inaturalist.org/taxa/130222-Bombus-melanopygus
Typically, these are the first bumble bee colonies to finish, with the nests collapsing by early summer. The typical life cycle is a single queen starts a new nest in January-February. This nest grows until the colony makes a new batch of queens and males and then the nest collapses. I typically get a lot of calls about this nest in May-June. So to find a nest in December is highly unusual.
To start, can you let me know where in the state are you located and if this bumble bee looks to be the one you are seeing?
If the nest is somehow hanging on from the summer (because we still have not had a cold snap) then I expect the nest will be ready to clean out for the chickadees. If it is just starting then the nest won't vacate until the spring. But get me some information and we can take it from there.
Hi Andony,
Yes, that is the bee! We live in Eugene. My husband took the birdhouse down in Oct. and when he pried the roof off with a hammer, he discovered the nest inside. It's possible that the bees were in the nest all summer and we just didn't notice them. So it could be hanging on from summer because we still haven't had a heavy frost. The birdhouse have been sitting on our picnic table on the covered back porch since Oct. and there is constant activity of bees going in and out. There are more bees now than there were in Oct. There is a thick liquid oozing from the bottom of the birdhouse.
Thank you for any help you can give us!
Nancy
Thanks, Nancy,
Let's connect via email. I will see if I can get someone over there next week. I am really curious what is going on. Send me your address and number to <personal data hidden>.
Let's connect via email. I will see if I can get someone over there next week. I am really curious what is going on. Send me your address and number to <personal data hidden>.
