The Leafcutter Diaries 3 – Balsam Days

One day while watching our Leafcutter, I realised that her behaviour had subtly changed.  Usually her foraging trips were short – she would leave to collect pollen and nectar and then return only a couple of minutes later.  Now her trips were 15-20 minutes long, and when she returned she’d started to land and rest near to the beehouse for a couple of minutes before resuming her nest building activities.

Her appearance had also turned a touch ghostly.

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Despite her now distinctly mouldy looking appearance I didn’t panic – I had seen this before in honeybees.  Our Leafcutter had found a patch of Himalayan Balsam somewhere.

Himalayan Balsam is a striking, pink flowering plant which grows to about 2m in height. It was introduced to Britain in the 19th century as an ornamental plant.  Unfortunately it is now one of the UK’s main invasive plant species.  It very quickly colonises and overcrowds native species, killing them off.  Despite it’s pretty appearance, it’s a bit of a thug – our apiary backs onto a riverbank where Himalayan Balsam grows, and each year we find strands of it growing straight through the concrete apiary floor.

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It’s very common on waterways – it is found on all of Lancashire’s main rivers.  I don’t have a major river near the house, but there is a brook about ten minutes walk away – this would also explain the increased length of our Leafcutter’s foraging trips.

At first thought, it seems odd.  Why would a bee expand so much energy flying to a plant some distance away, when there were perfectly good alternatives nearby?  One of the reasons that Himalayan Balsam is so successful in dominating other species is that the nectar it produces is so beloved by bees.  Given the option they will choose Himalayan Balsam over most native species of plant.  And when entering the flowers to get to the nectar, they are covered in the plant’s white pollen – which they then take to another Balsam flower.  Therefore Himalayan Balsam has evolved to ensure that it is very well pollinated – at the expense of the nearby native plants which suffer decreased pollination and therefore slower growth as a result.

While not a notifiable invasive species like Japanese Knotweed, it’s now widely recognised as a problem and parks, nature reserves and estates try to keep it under control by holding ‘balsam bashing’ days.

While I’m not the greatest fan of Himalayan Balsam for the reasons outlined above, our Leafcutter certainly seemed to be thriving on it.  She very quickly finished another nest tunnel.

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The Leafcutter Diaries 2 – 8th July

I’d seen ‘our’ Leafcutter roosting in the beehouses for a few weeks now, but tonight was very happy to see that she’s started nesting there!  As I went out into the garden after work one night I saw her going to and from the beehouse, returning each time clasping a section of leaf before taking it into the tunnel.

I grow a rose bush in the garden especially for Leafcutter bee nesting material – I’d read that rose leaves are their preferred choice when constructing nests.  I’d been watching this carefully to spot any signs that it was being used with no joy, and each trip the bee made to fetch leaves was very short – with only a minute or so between her leaving the beehouse and returning.  So where was she going?

It didn’t take me long to find the answer.  About 6 feet away from the beehouses is a Snowberry bush, and this showed the tell-tale signs that a Leafcutter bee had been at work.

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That night I also managed to get a shot of our Leafcutter bee-hind, which meant that from this and her size I could finally identify her as a Wood-Carving Leafcutter Bee (Megachile ligniseca)

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I staked out the beehouse over the weekend and managed to get a shot of her bringing a leaf back to the nest.

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I thought she must be getting close to finishing this nest as she seemed to be ‘auditioning’ new tunnels in between completing the current one, flying around the front of the house to view all the options and popping in and out of tunnels for a closer look.

Then by the end of the weekend, she’d finished!  Leafcutters always seem to like to finish a nest off by sticking a full leaf to the front for a final flourish.

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Leafcutter Diaries 1 – 21st June 2017

Every evening when I get home from work one of the first things I do is head on out into the garden.  I love to potter around for 5 minutes of so, filling the bird feeders and checking out what’s been going on – it gives me some much needed reprieve after a long day at work and busy commute.

Today as soon as I opened the door I could hear a strange crunching noise coming from the bottom of the garden.  I headed down there and found the source of the noise at the beehouses.  One of the houses I made this year was a bit of an experiment and uses dry plant oasis as the nesting material.  It was this house the sound was coming from.  I made myself comfortable and waited.

As it happens I didn’t have to wait long before the culprit emerged – a Leafcutter bee!  She was entering each hole and chewing them to make them precisely the right size for her.  Every couple of minutes she’d back out of the hole, pushing the ‘spoil’ out behind her as she went.  I ran for my camera and managed to get a couple of shots but the combination of the dull evening light and her frantic activity meant that these weren’t the best.  All the same, I wanted to record this.  We’d had Leafcutter bees in the garden before foraging, mainly the smaller Patchwork Leafcutter bee (Megachile centuncularis), but this was the first time I’d ever seen one near the beehouses.

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This Leafcutter seemed larger than the normal foragers though.  I knew there wasn’t much possibility of being able to ID her (she had to be female as the chewing is nesting behaviour) due to the amount of oasis she had stuck to her body.  I’d just have to hope she found the accommodation on offer acceptable and decided to stick around!

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Goth Bumblebees, some unlikely garden visitors

A couple of weeks ago I returned home from work to find that my mother-in-law had been trying to reach me.  The reason?  Her window cleaner had reported that there were bees in a bird box attached to the side of the house, and she wondered if I could help find out what they were.

Without even seeing them I was pretty certain of what they would turn out to be – Tree Bumblebees!  The window cleaner had said they definitely weren’t wasps, and a nest box is too small for Honey Bees to set up home in, so Tree Bumblebees were the most likely candidate, as they are a species that particularly love bird boxes.

Tree Bumblebees are a species that’s relatively new to the UK, having first been spotted in the South in 2001.  In the years since, they have spread to colonise much of the rest of England and part of Scotland.

Their rapid spread across the UK has been put down partly to their adaptability – they forage on a wide range of flowers and are aerial nesters who are not too demanding in terms of suitability of nest sites.  Oh, and the fact that in the UK we love our bird boxes, which are reminiscent of a Tree Bees favourite nesting spot – a hollow space within a tree.  This means they love urban gardens and are a frequent visitor to many.

Tree Bumblebee recorded sightings 2007, from the NBN Data Gateway – 2007

Tree Bumblebee recorded sightings 2016, from the NBN Data Gateway –2016

I went round the next day to take a look, and verified that they were Tree Bumblebees.  The male bees swarming around the entrance hole was a dead giveaway – behaviour that is common at this time of year as male bees hang around hopefully to see if an un-mated Queen will emerge.  My mother-in-law is not the greatest fan of bees, mainly because her daughter is badly allergic, and as the box was just outside her patio door their presence meant she was prevented from being able to leave the door open in the heat.  So I quickly volunteered to move the box containing the nest to my garden a mile down the road to look after for the rest of the season.

That weekend we waited until after dark to move the bees.  We arrived armed with a sponge which I used to block the entrance hole before removing the box from the wall.  Then we undertook a fairly nervous car journey with the nest encased in a carrier bag – an insurance policy in case the sponge fell out!  The bees within buzzed loudly as they knew something was up.

On returning home I quickly hung the box up on a nail I’d stuck in the side of the garage earlier.   The sponge was left in place – if it’s removed in the dark the bees may emerge and then not be able to relocate the nest.  I went to bed that night happy that the move had gone well, but worrying about whether our new garden tenants would have enough oxygen within the nest to see them through the night(!)

The morning came and to our surprise, the local male Tree Bumblebees had located the nest and were beginning to swarm around the entrance.

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I nervously removed the sponge blocking the entrance hole to the sound of the now familiar buzz rising as the bees inside felt the nest box move.  I was convinced that the bees would pour out to see who or what was interfering with their home so beat a fairly hasty retreat, but only a couple flew out.  They immediately began taking orientation flights – flying in larger and larger circuits around the garden and then returning to the nest before setting out again.  This allows the bees to map the location of all the local landmarks (specific plants, the compost bin etc) which will allow them to find their way home again.

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It was a couple of days later that I finally got a closer look at our new guests.  And I got a bit of a surprise – Tree Bumblebees are a very distinct bee with a bright orange thorax. There’s no other UK bumblebee that looks like them so they are very easy to identify.

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There are more uncommon Melanistic variants though, where the orange is either faded or missing, meaning the bees are almost completely black.  And that’s what we had!

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They are really stunning, and of course their unusual attire means I have to call them ‘Goth Bees’.

They have now been in the garden for a week, and seem to be getting used to their new surroundings.  On one particularly hot day this week I arrived home to find a group of bees clustered around the entrance hole, using their wings to fan warm air out of the nest.

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These bees are excellent thermoregulators, fanning the nest to cool it if it’s too hot, or clustering together and using their flight muscles to ‘shiver’ and raise the temperature if it’s too cold.  They keep the temperature within one degree of 30 degrees centigrade at all times.

Many more male Tree Bumblebees are visiting daily – some days there are too many to count.  The females can get quite grouchy about this – yesterday I saw one female repeatedly grab male bees and physically fly them away from the nest.  It didn’t seem to stop the tenacious males returning, however!

The fact that the males are here means that it’s almost the end of the season for this nest. The new Queens will emerge and mate, before leaving the nest for the final time and hibernating until next year.  The bees within the nest will die off and the Tree Bumblebee cycle ends for this year.  My father in law can then have his nest box back! I’m going to miss these little bees once they are gone, so I’m going to site an empty nest box in this location, containing a little moss and animal fur to encourage Tree Bumblebees to inhabit it next year.  Who knows, maybe one of this year’s new Queens will take up residence?

It may only be a few weeks now that I get to spend with these bees, so I’m going to make sure I enjoy them while I can 🙂

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