Thursday, 25 April 2013

Range expansion of the tree bumblebee


By Liz Elliott

My PhD focussed on modelling the range expansion of species and I often used butterflies as examples of species expanding their range in Britain but I didn’t know much about other pollinators and so I thought it would be great to do a bit more research into this.  The first species that sprung to mind to find a bit more about was the tree bumblebee (Bombus hypnorum).  Until 2001 this bee was not present in the UK, which was surprising as it is widespread on mainland Europe.  The first sighting was made in the New Forest and since then this bee has rapidly spread around the country with sightings from Northumberland to Wales and Cornwall.  Have you seen a tree bumblebee near you?  If so help BWARS to map its spread by visiting: http://www.bwars.com/index.php?q=content/bombus-hypnorum-mapping-project

The tree bee is easy to identify as it looks very different to other bumblebees with its ginger thorax, black abdomen and white tail, and (helpfully for ID!) the queens, males and workers all have the same colouring although vary in size.  The queens of this bee emerge from hibernation in February or early March and workers are active throughout spring.  Males are produced in late May and June and a partial second brood may be active in the summer. It is possible for sightings of late flying queens to be made into November and December, so you may spot this bee out and about nearly all year round!

Identifying features of the tree bumblebee
  
This bumblebee is found in a wide range of habitats, including woodlands, gardens and parks.  Unlike other bees in the UK, which nest at ground level, this species nests above ground in cavities, such as holes in trees and roof spaces, and indeed last year at Leeds University a nest was observed in a gap in one the buildings in the Biology department!  The tree bumblebee is also often found nesting in bird boxes, so even if you don’t have birds nesting in your garden, a bird box could be a really important nest site for these bees instead.

Nesting in a bird box in an allotment in Leeds - can you spot the bee zooming in on the entrance?!
The nest in the Biology department at Leeds University - a little blurry but you can just make out a few in the gap in the wall.

A nest in a garage roof.
 
The males of this bee do a dance outside nesting sites, waiting to mate with the new emerging queens.  Last year the Leeds team were lucky to observe this behaviour outside the nest in the garage roof.


Males dancing outside the nest.
 
Bees are really good to encourage into your garden and the tree bumblebee in particular is an important wild pollinator of fruit trees and is often found visiting their flowers and those of other plants that produce fruit such as bramble and raspberry.  While out and about in Leeds we have often seen them on flowering currant, so if you have one of these in your garden have a look and see if you can spot a tree bumblebee on it – I had a look at the one in my garden and was delighted to find there were some on mine!

Tree bee feeding on a flowering currant (Ribes sangiuneum)
 
This bee is expanding its range when other bees are declining because it is often associated with open clearings in woodlands but also because urban gardens are a good source of readily available foraging and nesting resources.  It also has relatively high dispersal ability and so is able to fly between patches of suitable habitat.  This high dispersal ability may be how it colonised the UK, flying across the English Channel, potentially with the aid of strong winds.    As this bee has different nesting sites to other bumblebees in the UK it is not competing for resources and so is unlikely to impact negatively on other species.  The rapid expansion of this species may mean that it will soon be found across the whole of Great Britain, so watch this space!

We rescued this rather drowsy tree bee from somebody's drive earlier this week!


21 comments:

  1. 1 july 2013
    Hi,

    We live in essex, Stanford le hope, and have a tree bubblebee nedt in our roof extension by our outside guttering. AMAZED!!

    ANY ADVICE MUCH APPRECIATED

    THANKS

    THE WILLIAMS FAMILY

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  2. Can't confirm but I believe that I have just seen my first Bombus hypnorum queen in SE Northumberland. I'll keep looking

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    1. That would be great. They are moving northwards and last year one was seen in a Scottish garden. If you see the bee again and can confirm your sighting you can report it to the BWARS Bombus hypnorum mapping project: http://www.bwars.com/index.php?q=content/bombus-hypnorum-mapping-project

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  3. They are back! Two years ago they nested in the blue tit box, but the bad summer pretty well destroyed any chance of success and the nest basically died. No sighting last year, but they are now back in the blue tit box. New Milton, Hants

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    1. Great. Hope they are successful this year, the spring looks promising so far :-)

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  4. just went to the compost bin to put in some old teabags, l seem to have upset some bees ! buggers stung me !! closer investigation revealed a load of tree bees in and out of a tiny hole in the emptying flap

    tony
    hethersett,norwich

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  5. the bee sat on my hand as I was driving down Regent Street, central London on the afternoon of May 10th. Very cure and friendly. Probably got in where I actually live in SE London by wild and leafy Nunhead cemetary
    tried posting this before but it didn;t go up - sorry if there are two

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  6. Hi Howard here in NW England. Just identified Tree Bumblebees in a tit box in my Timperley, Altrincham, Cheshire back garden. Really pleased. No wonder the tits decided to nest in a nearby concrete tit box instead ths season!

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  7. Tree bumblebees in a nest box in Rowton Chester, lots of activity.

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  8. Tree bumblebee nest in my roof in Lincoln. 20 or so dancing males outside my bedroom window every morning! Worried at first but now I've identified it I feel better, thanks to this site.

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  9. So we live in Pudsey and have a Cotoneaster Horizontalis which has been covered in tree bees for the past few days. I identified that they have nested in our or next doors roof space as they were doing the dance outside this area as described above. Are these bees safe to live with? We don't want to kill them but we don't want to fear attack by swarm either??

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    1. Yes, bumblebees are safe if you do not disturb them in their nest. Bumblebees are normally very docile and non aggressive and are focused on foraging for nectar and pollen and not on bothering humans. Bumblebees only live for a few months and by late summer all except the new queens should be dead and the nest abandoned. Bumblebees normally do not return to their old nest and choose a different one in the next year.
      So just leave them be, watch and enjoy them.

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  10. Thanks UP admin! We will enjoy them :)

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  11. Howard of Timperley here again. The tit box is busy and stained with yellow pollen. Q - Should I clean the box out in October for tits next season or leave it until early spring? Or maybe leave it alone?

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  12. Yes it would be best to clean it out with hot water in October or November. If you want you could put in some dry moss or leaves so it is nice and cosy for any bird sheltering in there on a cold winter night.

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  13. I assumed we had some kind of bees nest in our roof last summer. This year they have returned and after doing some research (with the help of Google) stumbled upon this page and can now identify them as tree bees as I often watch the males 'dancing' outside of the nest. Although I've only just learned that's what there actually doing :)

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  14. Also,the nest is in my son's bedroom wall..I can hear them realy loud in his room especially during the night. Should I be concerned in any way?

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    1. The bumblebees are harmless if you don`t disturb the nest. If you leave them alone they will normally not bother you. The nest will only be there for several months and all workers and the old queen will die in summer/late summer. Only the new queens survive but they will leave the nest.

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  15. We have one in St Helens, Merseyside.
    My next door neighbour had 2, one in his bird box and one in his shed.
    They are so adorable and that dance is amazing.
    Yay for the bees :D

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  16. I have a very busy white cotton bumble bees nest just under my roof. I've taken a photo and counted 47 bees. it's June and I expect it to grow in size as the season progresses. Really rather pretty, especially when many of them get caught in a slight breeze and quickly find their way back to the entrance. Northamptonshire

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  17. Have these bees in Leeds, they have managed to get in through a hole where my drain pipe sits and either spread through the wall cavity or have 2 nets as there is about 40 of them dancing about the roof tile above the bathroom window.

    Where the drain pipe hole is it must be the female ones? they come and go every so often but it's where my 2 year old plays out and she would be in the way of them coming and going. Also where our bathroom ceiling curves down closer to the tiles usually mid afternoon you can hear what sounds like thousands all buzzing away.

    this has resulted in having to keep all the back windows of the house shut bathroom, landing and back bedroom as well as the patio door that lead out from our living room as we are getting them in the house one day I had to remove nearly 20 odd of them so for this reason I have had to call the local council who are coming to sort the problem next week.

    I've also got small groups of dead bees around garden and noticed today stood watching from a distance that the male bees I can only assume seem to fight each other as a couple dropped to the floor from roof high and were scrapping on the floor before flying back up again.

    I can't really risk my daughters getting swarmed incase she upsets them.

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