Bird Boxes & Bumble Bees 39

Tree Bumblebees

Our Honeybee Swarm Collection Coordinator provides this update to his advice first published last year about dealing with the newly arrived Tree Bumblebee that has a particular preference for nesting in bird boxes and can be very aggressive if disturbed or provoked ….

Bird boxes and the tree bumblebee (bombus hypnorum)

Both the above are now widespread in the UK. The problem is that the latter regards the former as its favourite nest site, and will aggressively defend its nest. Bird boxes are now very popular, and frequently given as Christmas presents. They are often fixed to houses, fences, or garden sheds, in order to attract garden birds.

For many years we have received calls about bumblebees nesting in bird boxes. However, we now have a dramatic increase of this new – to the UK – form of bumblebee, the tree bumblebee (bombus hypnorum), which particularly loves to nest in bird boxes.

Bombus hypnorum male on Cotoneaster JEREMY EARLY(1)For recognition purposes this bee can be distinguished from other bumblebees by its tricolour banding, with: (1) tawny red or ginger head and thorax; (2) charcoal grey or black abdomen; and (3) white tail. Photo (left) by Jeremy Early is of a male feeding on cotoneaster in his Reigate garden, from his book “My Side of the Fence”.

The spread of this species has been staggering, and with a huge human impact, since these bees favour domestic buildings and structures, requiring only a small cavity as nest space – with bird boxes as their preferred choice. The trouble arises because unlike other forms of bumblebee (which are generally docile), the tree bumblebee is easily provoked, and can often be aggressive, buzzing and even stinging people who stray close to any nest near a pathway, e.g., by a door, porch, fence, or garden shed. The risk of conflict with humans in this situation is greater if the box is fixed below head height, and, worse still, liable to vibration, which the bees hate (e.g., on a wooden garden shed, which rattles whenever the door is opened or closed).

The result often is a distress call to a beekeeper about a “swarm” of bees. But, unlike the honey bee, the tree bumblebee, as all other non-honeybee forms of bee, does not swarm, cannot be hived and in any case has only short-lived, annual nests; typically from April to June when their nests are most active.

The speed of the spread of this species across England and Wales – probably soon to reach Scotland – is remarkable. Yet this bee was only first recorded in the UK in Wiltshire as recently as 2001, having arrived probably from the continent. In Surrey it was first photographed at Egham in 2004, and later in Reigate by Jeremy Early as illustrated in David Baldock’s “Bees of Surrey”, published in 2008, when it was still described as a “rarity” in the County. However, by 2011, as Clive Hill noted in an article in the British Beekeepers Association (BBKA) newsletter – BBKA News (No. 189); the species had already become familiar to many beekeepers in England and Wales, as the cause of phone calls about “bee swarms” in bird boxes.

This is borne out by Reigate Beekeeper’s swarm statistics for our own catchment area (most of South-East Surrey) fom 2007, with no recorded cases in my swarm records from then until 2011, when I first recorded three cases. In 2012 this total shot up dramatically to 22. The next year, 2013, the total grew to 25, with four bird box removals, including two from school premises. Last year, 2014, the total exploded to a record 95 calls, with a huge surge in May – when some of our swarm collectors received 10 or more calls a day about this species, and local pest controllers even more.

Moving a Bird Box full of Bees

Investigating  incidents of bees in bird boxes takes time – and diverts us from our intended task of dealing with honey bee swarms. Moreover, moving these boxes when full of bees, as I can confirm, is not straightforward. The move has to be done at night, after the bees have stopped flying and are back in the nest. This means working in the dark, because this species will fly until then, later than honeybees. Then you have to wear protective bee gear in order to avoid being stung, working with a red light from a cycle rear lamp, because otherwise the bees will come out immediately if you shine a normal torch on the box. Before detaching the box from its fixing, you must first stop up the entrance, and then tape up all gaps and cracks – all of which may not be easy if the box is rotten or in poor condition. And then you will have to detach the box, which again may not be easy if it is nailed or screwed in. Finally, you will have to relocate the box to a chosen site, fixing it to a firm surface which is not liable to vibrate. If you are moving the box nearby (i.e., less than a mile away), you should delay removing the entrance bung for a few hours the next day to help the bees realise that they have been moved and need to re-orientate. All very laborious….

However, as already noted, time taken in dealing with these bees only diverts us from our main aim of catching honey bee swarms. Moreover, as volunteers and hobby honey beekeepers, we cannot be held responsible for this or other (i.e., non honey) forms of bee. Above all, we are not insured under our BBKA insurance scheme to deal with tree bumblebees, since this cover only extends to acts undertaken by us as part of our normal (honey) beekeeping activities.

For all these reasons, while trying our best in answering phone calls to help identify this species, and advise about their habits and lifestyle, we cannot become involved in their collection or removal. This accords with BBKA advice on its website, which states:

Please do not call our beekeepers about bumblebees. They are unable to help you with these and will not collect/remove them. For advice on moving bumblebee nests please go to the Bumblebee Conservation Trust  website where you will find a great deal of information.”

Meanwhile, some  hopefully timely advice to follow.

As a rule tree bumblebee nests become active in April, and can remain so for about two or three months, or even through to autumn, if the Queen rears a second colony. So now – winter or early spring – while the boxes are empty is a good time to take precautions, to reduce the risk of these bees setting up home there later in the year and creating  a nuisance – and trouble for the swarm team!

What practical steps can be taken to achieve this?

  • First, ensure the box is clean inside. In the case of an existing box, first take it down and open it up, to clear it of any debris from previous nesting material, and then thoroughly clean it. This will help attract birds to nest.
  • Secondly, before (re)siting it, ensure that the box is well positioned for birds – see
  • Thirdly (most important) avoid placing the box either (1) near a footpath or passage way; or (2) at or below head height; or (3) on a surface or structure liable to vibrate.

By following this advice now, you should reduce the risk of a tree bumblebee invasion of your bird box later in the year. Moreover, even if they do nest there then, you will have reduced the risk of their becoming a nuisance to yourself or your family, visitors, or neighbours.

In this way you can have the benefit of their pollination, and the pleasure of watching them, without the risk of you or others then being molested or stung by them – or having to call out a swarm collector!

Richard Woodhouse 9th February 2015


  1. I’m Christine, my boyfriend made me a lovely decorated bird box. I had a colony of tree bees taking up residence. It was fascinating to watch them coming and going, u will see 2 tree bees buzzing outside which they r guarding the nest against predators. But if u interfere with the tree bee guards they will attack u u as I found out and got stung. I had never heard of them till I had them nesting in my nes bird box.

  2. That happened to me last summer, I had tree bees nesting in my bird box. But sadly they flew off and have not come back this year. I bet u have tree bees in your bird box.

  3. Hi we have tree bumble bees in our blue fit box and they appear to be sealing the hole from the top downwards what’s this about ?

  4. Very useful advice Richard. We have a new tree bee colony in our bird box and we shall try to accommodate them this season out of natural curiousity. We were attaching a plastic mesh for our climber plants with ‘u’ nails and disturbed them but they have settled down.

  5. I was under the impression that they are the males that are flying around at the entrance waiting for the queens to appear to mate. The males do not have a stinger. Is this correct?

    • Ah, now … you are asking a Honey Bee Keeper about the life style of Bumblebees? I believe you are correct in that drones would ‘loiter with intent’ at the entrances to a bumble bee nest, but its too early in the season to be seeing that yet.
      New queens are only produced at the of the summer, when they fly out, mate and then each newly mated queen seeks a suitable secure place to overwinter by herself … to emerge the following spring and start a new nest. Meanwhile all the bees, including their queen in the the original nest die out.
      Interestingly, old bumblebee nest sites make great nests for mice looking for somewhere to overwinter. And when the mice leave that nest in the following spring, queen bumble bees, that had been overwintering, by themselves move in to build up their own nest …and so on ….

    • They do sting as last year I had tree bees in my brand new homemade bird nest looking all pretty for a bird to nest in that my joiner bf made. Along came all this buzzing outside above my back door, However, I stood on a chair to try to have a look which was quite stupid. The tree bee guards stung me. They buzz around the hole to protect the queen. Sadly they have not come back this year, but were fascinating to watch.

  6. Really helpful information, thanks. I noticed some buzzing last week and video’d them around a bird nest as a swarm of honey bees from a neighbour’s garden had recently been removed and resited and I wondered if it was a new queen setting up another hive but I could see they didn’t look like honey bees. I’ve taken a photo and they’re the same as your picture above. I’ve just been gardening near them as I thought ‘bees don’t sting unless threatened’ but think I’ll now give them a bit more distance. I’ll leave them where they are as they’re not affecting anyone but I will clean the bird nest when I can see there hasn’t been any activity for a while, lol quite a while!

  7. Fascinated to see our bird box appears to be full of bees this year! It’s a hive of activity! They got a bit upset when I cut the grass near them – but soon settled down again. We shall enjoy watching them from a distance.

  8. Hi , I noticed yesterday that I have bees coming in and out of my swift bird box and flying around outside of it , will this effect the swift from coming in the box , and will the bees sting the birds ?

    • You have a coloney of Tree Bees nesting in your bird box. Its doubtful your Swift will nest in its box as the bees will attack the bird. I had Tree Bees last year in my new bird box, it was amazing to watch them buzzing in/out and also outside of bird box they normally have 2 tree bees on guard. Come autumn they had left. Sadly they have not come back this year.

  9. Got bird box in garden full off bee’s. Moved it but some of the bee’s are still buzzing around were it was previously.will they settle eventually.

    • Yes, the bumbles buzzing around would have either been bumbling about when you moved their home (did you move it during the day while some could have been flying?) or had failed to notice it had moved when they left home to go to work in the morning after you moved it! They will disperse during the day, either finding their home again or gate crashing another nest.

  10. Have a very busy nest of tree bumble bees in a bird box situated in our apple tree.
    They Are constantly swarming round it and first noticed a week or 2 ago ( beginning of may).
    Will watch from safe distance and the little children can’t reach do hopefully safe.
    We are in West Lancashire.

  11. Thankyou for clear good advice, very informative. I will enjoy watching them but leave well alone . This is the second year I have had a nest box being taken over by bees .

  12. Thanks for this information, very useful. I had no idea that these were non honey bees! Good to know they are here till June!! I don’t find them particularly aggressive but will treat them with respect!!!

  13. Thanks to this article I managed to confirm tree bumblebees in one of my bird boxes. Can definitely confirm they are in Scotland in the Glasgow area

  14. Whilst furloughed I am taking advantage of lots of time to sort out my garden – including painting fences. It became apparent very quickly that there is a nest of bumble bees – I suspect tree bumblebees – somewhere on the neighbours side of the fence. It looks as if they were coming from the bird box mounted on the fence.
    Because I was painting, the fence was moving and the bees became quite agitated and “dive bombed” me until I retreated.
    I don’t want to disturb them – and certainly don’t want to ask neighbour to go to trouble of relocating the bird box. But would really like to finish painting the fence before I return to work in a couple of weeks time.

    Is there a time of day that I can continue my work without disturbing the bees too much? Or anything else I can try? I only need a couple of hours to finish the area. Or am I going to have to wait until later in the year when they leave to finish off this part of the Fence?

    • I fear that the bumblebees will be rather active as long as its light, warm and dry enough for them to fly. Qualities that you will no doubt also need for painting the fence. Added to which they will not be appreciating the smell of the paint!
      If the bird box is reasonably robust and ALL bee sized openings and gaps are able to be temporarily sealed, there are perhaps two options.
      1. temporarily relocate the bird box (preferred) or
      2. seal up the bird box in situ for a few hours.
      Either would require the bird box to first be sealed up during the night using red light ONLY to see what you are doing. No patio lights or full moons!
      If relocating, once closed up, immediately move the box as far away as feasible and secure it before unsealing after an hour or so and retreating to a safe distance! Repeat a following evening to return the box to its original site after having painted the fence.
      If sealing and leaving in place, ensure that adequate bee-proof ventilation is maintained for the bees within the box otherwise they WILL overheat and perish … and make a lot of distressing noise in doing so. As soon as you are able after an early morning session painting the fence, safely and efficiently re-open the bird box at looooong arms length.

      • I would not deal up nest hole its cruel, u have tree bees that always nest in bird boxes as they love making their home there. However, Tree Bees have Tree Bee Scouts hoovering around nest box, normally theres 2 Tree Bee Scouts. This I know as fact as I had them last summer, nest box was just above my back door they never bothered with me and were just so fascinating to watch them going about their business. If u try to move box, they will go for u.

      • Thanks guys.

        I braved the bees wrath! Lol.
        I went out at 6am to see if they would be awake yet and got a good hours painting done before they warmed up. There was a bit of occasional irate buzzing as I simply couldn’t paint fence without moving the bird box to a degree. But no-one left the nest. When the buzzing became more constant i retreated for the day.
        2 mornings like this (with a few days in between to ensure the bees weren’t too distressed) and the jobs done. They appear none the worse for any fumes or for my disturbances and are still seen every day buzzing around the entrance to the bird box. Certainly I’m sure it was less stressful than trying to relocate them even temporarily and they weren’t forced to stay inside at any point.

        Thanks for the help

  15. I have a colony of Tree Bumblebees nesting in my newly fancy decorated bird box my b.friend made for me. However, I didn’t realise what they were till I looked it up. Do tree bumblebees make honey. I’m happy they chose to nest here and r fantastic to watch as they search around the nest.

    • Hi, the bumble bees will make limited amounts of honey but only sufficient to feed the brood in the nest. The colony itself would not survive the winter, with only a fertilised new Queen overwintering in a secure and warm nest she makes for herself. There is no need or ‘drive’ for bumblebees to overproduce and store honey, as honey bees do.

      • Thank you for your reply about my tree bees nesting in my new bird box my boyfriend made me end of summer. However, do these types of bees stay & hibernate like now. Or did they fly out when I was’nt looking.

  16. After a talk at our Ladies Lunch Club by the delightful, exuberant Brigit Strawbridge, expert on Bumblebees, I am thrilled to have Tree Bumblebees in my partner’s garden in Barnsley. Fascinating watching them in the bird box, lots of Photo’s and many visits. Watch out for her book on bees – September, 2019. Has inspired me to create a bee-friendly lawn garden.

  17. Not sure when this article was first published. I have a bird box full of bees in Fife Scotland so looks like their march north has began.

  18. Good to know the bees will leave the bird box when Autumn /Winter arrives so will just watch them buzzing around until then

  19. I have got a nest of bees in my bird box, but can’t get close enough to see what type they are. Is the default position that because they’re in a bird box they are tree bees?! I’m only worried as I have a very small garden & 2 young children and have read that this type are particularly aggressive.

    • Honey bees would not ‘nest’ in a typical bird box because such boxes are just not large enough for a viable colony to establish and develop. What you are seeing would almost certainly be bumblebees, but not necessarily Tree Bumblebees. However the same approach to safely moving the box to less troublesome location would apply. See our post … Bird boxes & Bumblebees
      Unfortunately as Beekeepers we are unable to directly intervene.

  20. Hello we had bumble bees in a bird box on front of our shed they were no bother they got quite active early July then seemed to have died off early August they were black with red abdomens

  21. We have a similar situation with a multiple hole nestbox meant for sparrows .last year the central hole was used by bluetits but this as been occupied by small black bee’s with a red rump .sure they were mentioned on spring watch are they alright to leave where they are.

    • Hi Bev,
      Your description certainly suggests that Red-Tailed bumblebees (Bombus lapidarius) have taken up residence in your bird box – although their ‘expected’ nesting sites are supposed to be in old burrows or under stones. The female red-tailed bumblebee is a very large, black bumblebee with a big red ‘tail’. Males are smaller and, as well as the red tail, have two yellow bands on the thorax and one at the base of the abdomen. There are two other similar species of bumble bee, but both are much rarer.
      As with other social insects, the queen emerges from hibernation in spring and starts the colony by laying a few eggs that hatch as workers; these workers tend the young and nest. Males emerge later and mate with new females who are prospective queens. Both the males and old queen die in the autumn, but the new queens hibernate.
      As long as the comings and goings of the bees are not a problem for yourselves, (or your activities are not posing a problem for the bees!) then they can be happily left to get on with their work.
      We would recommend that bird boxes are located well above head height (and away from open-able windows) when close to human occupation. If boxes do need to be relocated, that is best done when not in use, by birds or bees!

  22. I’m actually thrilled that l have bees nesting in my bird boxes. They don’t cause a problem and lve worked hard to make my garden bee friendly. I have one nest that looks like its Bumbles and another with Tree Bees (?) also seeing lots of honey bees in the garden!

    • Perhaps an adaption of the definition of a weed is relevant …. A nuisance bee is only a useful bee in the wrong place.

  23. I have a camera in my bird box and on Saturday 14th April we had our first egg. I then spotted a tree bumblebee in the nest. This morning The egg had disappeared and a tree bumblebee appeared from under the nest material. I immediately took down the box and took it into the house. When I opened the box I could hear the bee but could not see it. When I uncovered the be it was very aggressively protecting the TWO eggs that it had dragged below the bedding. I got the bee out and killed it. I placed the eggs back on top of the bedding and now it is a waiting game to see if the great tits come back !!!! I had a swarm of these bees in a bird box in my woods last year and I was quite happy as I also keep bees mainly for pollination, I didn’t realise that they are killing our native birds. I don’t know if they lay a grub that eats the eggs or waits until they hatch but would be interested to find out!!
    Malcolm Clark

  24. Wow fasanating! My neighbour has these. I went round last night and took photos and a video. She said they went there two days ago. We live in the hg1 area of harrogate. Must go and show her this.

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