An experimental Bee House

Last year, I watched, fascinated, as Mason Bees (Osmia bicornis) made nests in tubes in a commercially produced Bug House situated in a local community garden, the Leechwell Garden. This Bug House is meant to be educational and so has been placed in a prominent position. This brings with it the risk that it will be subject to some attrition; indeed the removable tubes were tampered with both last summer and this spring and the Bug House was knocked off the wall twice during the winter.

I wanted to build another Bug House for the Leechwell Garden to be put in a less vulnerable place but it proved impossible to find a suitable position. I went ahead anyway and placed the new Bee House at the bottom of my garden which is about 100 metres from the Leechwell Garden (as the bee flies).

Experimental Bee House beginning of season
The Experimental Bee House at the beginning of the season (March 2015). I hope you can see the two vegetable boxes with the sides of the top one insulated with recycled vinyl floor covering, also the protective roof. Two cassettes with tubes are in place in the insulated top box . The garden still looks dormant although a few daffodils are visible.

 

My aim was that this experimental Bee House should be made from recycled materials so that it could be replicated by others at minimal cost. I looked around for suitable materials and one day as I was passing the Totnes shop of Riverford Organic, our local organic grower, I saw some vegetable boxes in the window. These looked ideal to make the body of the Bee House so I contacted them and they kindly gave me two boxes. The boxes were not fully sealed, needing insulation and rain protection, so I went to CarpetRight in Newton Abbot and they kindly gave me some samples of vinyl floor covering. I used these to insulate the sides of the new Bee House and to give it a roof. I found some logs, stones and bricks to provide ballast and stability as well as providing potential homes for insects. I sited the new Bee House so that it caught the early morning sun.

I wanted to provide tubes for the bees to nest in and had hoped to use inexpensive bamboo canes from the garden shop. Although I was able to cut up the canes, I found they were filled with soft material and unusable. I, therefore, had to buy solitary bee tubes from Wildlife World, my only outlay.

Experimental Bee House Cassette
One of the cassettes holding the bee tubes. The tubes are organised in to an old mineral water bottle and secured with a cable -tie. Four of the tubes contained mason bee nests from last year.

 

The tubes were organised in to cassettes. Each cassette was based on an old mineral water bottle cut down below its spout but long enough to protect the tubes. About 20 tubes were placed in to each cassette and these were secured using a cable-tie. I put out two cassettes in March, each containing four tubes with nests from last spring in order to give the new Bee House a start. A third cassette went out on May 28th when I thought the bees needed extra capacity but only two tubes were filled.

Experimental Bee House end of season
The end of season view. In two cassettes most of the tubes have been filled, in one cassette put out later two tubes were filled. Some tubes where the seal was broken have not been refilled.

After I had made the cassettes I read that plastic is a poor choice because it is not breathable but by that time it was too late to change design. Despite this, the new Bee House seemed to have functioned well and many of the tubes were filled by hard-working female bees during spring 2015. This is described in the previous post.

Successes and failures with this year’s Red Mason Bees

As we humans continue our lives and perhaps savour the prospect of settled warm weather and holidays, the busy part of the year is already over for the solitary Red Mason Bee (Osmia bicornis). These important pollinators began their activity in early spring and have now built their nests and laid their eggs.

Last year I was fascinated to watch some of these bees in a Bug House in the local community garden (The Leechwell Garden). This year I kept a closer eye on this colony to try to understand their behaviour. I also built an Experimental Bee House at the bottom of my South Devon garden and watched the bees build nests. [I realise not everyone is interested in constructing new bee houses so I have described this in the next post.]

This week is Pollinator Awareness Week so it is especially important that we think about how to protect and encourage these pollinating insects.

The males emerge and misbehave

male Osmia
Male Red Mason Bee

 

Both Bee houses contained mason bee nests (in removable tubes or in wooden blocks) constructed a year ago. The removable tube nests overwintered in my garden shed and were put out again on March 6; twenty four filled tubes and some empty ones went in the Leechwell Bug House and eight were put in the new Bee House. The wooden block nests stayed out all winter as they are an integral part of the Leechwell Bug House; they may have suffered damage when the Bug House was dislodged from the wall.

Osmia on Bug House
Male Red Mason Bee resting

 

I watched the tubes carefully from mid March and was very pleased to get the first hint that a male had emerged when, on April 16th, I noticed that one of the mud seals had been broken. The day before had been very warm so perhaps that encouraged the bees. Over the next week, I began to see males flying about near the two Bee Houses. Fresh males are very beautiful: about two thirds the size of a honeybee and with long antennae, they have vivid orange abdominal hairs, a fringe of beige hair around the thorax and a very distinctive pale “moustache”. Some look a bit different: they have few abdominal hairs and look rather shiny.

Osmia shiny type
Shiny type

 

Osmia feeding from Forget me Not
Male Red Mason Bee feeding on forget me nots

 

The numbers gradually increased over the next two weeks and on sunny days there would be a cloud of male bees near the Leechwell Bug House (perhaps as many as 30) behaving in a very characteristic way. They would fly about, swinging from side to side rather like a metronome, sometimes stopping to look in to a tube, sometimes flying off to feed on nectar. They would also “bomb” one another, especially another male that had stopped to rest or to warm up. I saw one male try to pull another out of a tube and, once his friend was out, he tried, rather unhelpfully, to mate. The cloud of bees would work themselves in to a frenzy when it was very sunny or when a male/female mating pair was present, perhaps they could they smell other females.

Osmia looking out
It’s too cold for me ……

 

All this activity would stop when the temperature fell to 11oC or lower. The males would retire to the tubes in the Bee House, sometimes two or more in one tube where they would look outwards waiting until the conditions improved. Other bees such as the Hairy Footed Flower Bee continued to forage at this temperature and the disparity may have something to do with size, the larger insect being able to tolerate the lower temperature.

Some females and some mating

mating pair April 28 15 2
Mating pair with mites

 

Mating pair with other bees May 7 15
The stillness of the mating pair and the frenzy of the other males.

 

I didn’t witness any females emerging from their nests but I knew that had happened when I saw mating pairs on April 28th and May 7th in the Leechwell Garden. This was an exciting moment as it was a first for me. I was amused to see the female in the first pair decide to go walkabout; the poor male had no option but to sit there even when dragged in to a hole smaller than comfortable for two bees. My excitement was tempered by noticing many mites on the first mating pair which I suspect is not good news for the bees. The latter mating pair did not have the mites as far as I could tell.

Males near the end

worn out bees

Some of the males continued to patrol the Bee houses up to a month after emerging, ever hopeful of finding a receptive female. By this time they were wizened and black and didn’t look like red mason bees any more apart from their white facial hairs. Perhaps we would also look sickly if we fed on sugar alone. They disappeared altogether by the end of May.

Hard working females

yellow pollen
The first pollen-loaded female.

 

May 12th was another exciting day as I saw chrome yellow pollen on the floor of the Bee House at the bottom of my garden for the first time: I now knew that the females were busy building nests. The females are also distinctive and very beautiful, about the same size as a honeybee and larger than the male with, on their head, two horns which they use for tamping down mud. They lack the pale “moustache” but like the males, their abdomen is clothed in vivid orange hairs when freshly emerged.

Female Osmia bicornis
Female red mason bee. The horns are just about visible.  Her colour has faded and a better view of a fresh female with her orange hair is seen in the mating pictures.

 

I watched the females returning after foraging, buzzing loudly and entering tubes head first. After a short time they reverse out, turn round and back in to the tube. I am not sure what is happening here but I witnessed the behaviour many times. Once this elaborate manoeuvre was complete they flew off for more. I also saw one female building a mud partition. She added mud to the inner surface of the tube and gradually, over several trips to collect mud, built the partition inwards keeping it symmetrical and circular before sealing it off.

Throughout the season, there seemed to be plenty of forage about and no shortage of mud for nest building. For both Bee Houses I saw females continuing to fill tubes in to the third week of June.

Problems

In both locations, the number of females seemed very low, especially as there were plenty of males. Last year most of the tubes and wooden block holes in the Leechwell Bug House were reused by females who cleaned out the mess before re-provisioning them. This year the females did reuse old tubes but seemed to prefer fresh tubes when available. In the Leechwell Bug House I saw only two females but they filled more than twenty tubes. Males emerged from the wooden block nests but none of these was reused. At the bottom of my garden there were at least four females and they filled twenty four tubes. In both locations, the mud seal on some of the tubes remained intact and neither males nor females appeared.

Osmia housekeeping
Housekeeping

 

End of season view
End of season for the tubes in the Leechwell Garden Bug House. Many are filled, a few have not been reused and a few have not been used at all.

 

I don’t know why this year has been less successful but I wonder if the tubes were tampered with at a critical time. I know that some were stolen last summer so I presume that, at that time, many of the tubes were disturbed. I also suspect that the tubes in the Leechwell Garden were tampered with again in March this year. Perhaps this double interference damaged the developing females. The Bug House also fell to the ground twice and perhaps the wooden block nests were damaged. Another possibility is that mated females were produced but decided to go elsewhere.

A third possible explanation would be that the old tubes had been infected with another organism that damaged the developing bees.

I opened up the wooden block nests to see if I could glean any information about these problems. None of these had been refilled this year, whereas last year they were all reused. The wooden blocks were very messy: I could see the individual cells made by the bees but there were no intact dead bees. The nests were filled with a brown dust although within this dust I could see dead larvae. It was also clear that in many cases the mud partitions between cells were still intact. There had clearly been a major problem with these nests and I suspect that they may have been infected. The bees avoided these nests so they seemed to know that something wasn’t right.

I am beginning to think that new tubes should be supplied each year to make life easier for the bees and to avoid build-up of contamination.

Now it’s important to leave this season’s nests so that the eggs can develop and grow in to larvae. I need to wait until late autumn before moving them.

Overview of the year

It’s been another fascinating season of Mason Bee watching and as before I have been enormously impressed by the hard work and ingenuity of these bees, especially the females. The males have only one purpose but they seem to do it well.

Watching these bees is not only a fascinating experience, it also makes you aware of the interconnectedness of the natural world. The bees depend on flowers and the flowers depend on bees. We mess with these relationships at our peril and perhaps we understand our own place in the world by realising this. The highlight of season for me was seeing the chrome yellow pollen for the first time. It signified that everything was working; females had mated and were visiting flowers to continue their species. Fresh yellow pollen has a colour like no other, it seems to glow with the energy of sunlight and signifies the unfolding spring.

Looking for the Long-horned Bee in South Devon

The coast path in this part of South Devon traces the edge of the low crumbly cliffs as they meander around inlets and headlands, keeping the sea at bay. For several miles eastwards beyond Prawle Point, the path is mostly flat so this is easy walking but not without interest. The sea is an ever-changing canvas of colours and seals sometimes swim near the shore. On the landward side of the path a succession of gently sloping arable fields is backed by steeply rising cliffs with rocky outcrops, giving the walker the illusion of being watched from above, if only by birds of prey.

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Looking across Horseley Cove to the coastal fields.  The coast path runs between the coastal fields and the low cliffs. The steeply rising hills with rocky outcrops can be seen behind the fields.

These coastal fields have been cultivated for centuries but for the last twenty years or more, management of the land has been directed towards supporting the nationally rare cirl bunting. This is a pretty songbird that, until the mid 20th century, was found in much of the southern half of the UK. Changes in farming practices, affecting the bird’s food sources and nesting habitat, led to a decline in the cirl bunting population and by 1989 there were only 118 pairs, confined to coastal South Devon. Since then, agri-environmental schemes have been promoted to support the bird. Spring barley has been sown on coastal fields and stubble left in the winter to provide food for these birds. Wide, uncultivated field margins allow tussocky grass to grow and insects to thrive, providing summer food. Nearby hedges are maintained as nesting sites. By 2009 the population had increased to 862 breeding pairs, a conservation success.

Male Cirl Bunting (from the RSPB)

 

The cirl bunting is only one of several rare species found here and many scarce insects find nesting sites along this stretch of the coast. I recently went to look for the long-horned bee (Eucera longicornis), a nationally rare, solitary mining bee that is reported to be found here.

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Just over two weeks ago, I drove to this remote part of South Devon and found my way down the very narrow lane to the National Trust Car Park at Prawle Point. The mid-morning sky was an overcast grey but, with only a light breeze, the air felt warm and humid. The car park is next to a nature reserve and one of the local residents, a lesser whitethroat, sang from a nearby tree as if to welcome me.

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Descending from the car park

A short stroll down hill took me to the coast path and I headed eastwards along the low cliffs. With the lack of sunshine, contrast was low and colours were muted, but there was still much to see. Unusually, I paid scant attention to the sea; I was more interested in the plants growing nearby. The seaward side of the path is marked by a distinct band of vegetation along the cliff edge. Sometimes this is a fringe of low grass with self supporting flowering plants: pinkish-white umbrellas of wild carrot; scrambling legumes including common vetch with its feathery leaves and pink flowers and the tiny white-flowered hairy tare. Further along, growth is more substantial with tall bracken and bushes, sometimes so dense as to obscure the cliff edge. This barrier supports climbing legumes including tufted vetch and, where the blackthorn is well established, provides good nesting for the cirl buntings.

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Commmon Vetch

 

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Hairy Tare

 

The landward side of the path follows the edge of the arable fields and their wide, uncultivated margins. The luxuriously green spring barley fretted in the light wind and, in the field margins, rough grass prospered together with more wild carrot and many leguminous plants including more common vetch. I also saw large mats of kidney vetch sporting a mixture of lemon yellow flowers and feathery- cushioned white seed heads.

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Kidney Vetch

 

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The coast path showing the spring barley, the wide uncultivated field margins and the coastal fringe.

Despite all this apparent fertility and forage, insects were keeping a low profile with the exception of a few small bumblebees. Eventually I came to an area of rich, tall bracken and low bushes growing along the edge of the cliffs. One section of this cliff hedge had been colonised by purple-flowered tufted vetch scrambling through the bracken. Something moving, possibly an insect, caught my eye and I paused to look more carefully. After a few minutes another appeared and I thought I saw the distinctive long antennae of the long-horned bee. I could also see pale brown hairs but the bee was moving about quickly making it difficult to be sure whether this was all just wishful thinking.

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Male long-horned bee on tufted vetch

I waited and an intermittent stream of these insects then passed through, some moving around quickly, some stopping to feed on the purple flowers. They were about the same size as a honeybee and I could see their impossibly long antennae, the very pale front of their heads and the fringe of beige hairs around their thorax. These were definitely male long-horned bees and it was very exciting to see them for the first time. According to Steven Falk, fresh specimens have russet coloured hairs which fade after a few weeks so the bees I saw must have been flying for a while. One of the passers-through had pollen-loaded legs so I assume this was a female but she didn’t stop long enough for me to be sure.

Long-horned bee 7

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This picture shows the pale front of the head

 

By now there was fitful sunshine and I began to be aware of the other sights and sounds around me. Through the curtain of bracken and long grass, the sea was visible, taking on a kaleidoscope of new colours as the weather improved. The urgent metallic sound of cirl buntings echoed around the surrounding hills and coming from below I could hear the plaintive cry of oystercatchers and the gentle soughing of the waves.

 

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The curtain of bracken and long grass

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Long-horned bees used to be found across the southern part of the UK but they have suffered a drastic decline in the latter part of the 20th century. The decline has been due to loss of suitable nest sites and preferred forage.

I visited Prawle Point on June 20th. The two “sunny” pictures (featured image and Coast Path near Horseley Cove ) were taken by Hazel Strange on June 18th.

Cogden Beach: a special and unusual Dorset place

A place of sea and sky. A vast shingle beach. A unique wild garden with spectacular flowers. Wave watching, walking, fishing, or just being alone with nature. This is Cogden Beach near Burton Bradstock in West Dorset in the South West of the UK.

It was a fitfully sunny but warm day in late May when I visited Cogden. I parked the car and descended towards the beach between dense stands of gorse, hawthorn and bramble and, once I had escaped the coast road-noise, the air was filled with birdsong. A very visible chaffinch sang from the top of a tree as if to salute the fine weather and the see-saw song of the chiffchaff echoed from the undergrowth.

View from road
The view from the coast road with the beach and the sea

Cogden is a place where you can literally “see for miles” and the distinctive outlines of Portland to the East and Golden Cap to the West were clear. Spread out ahead of me was the broad shingle beach, a yellowish-brown stripe cutting across my field of vision. Beyond the beach lay the sea, its mirror surface a steely blue, disturbed only by wavelets that glittered in the occasional sunshine as though a host of fireflies were dancing.

View east from Cogden
The seaward face of the shingle beach at Cogden looking towards Portland – with people fishing and walking

Eventually, the path flattened out and I made my way on to the shingle beach, hard work on the pea-sized pebbles. The beach near the land is broad and flat and relatively sheltered but eventually it descends steeply to the sea. This seaward face is a harsher environment as the bank is attacked relentlessly by a procession of waves and, in a strong swell, the pebbles move in sympathy, roaring as they go.

Cogden Beach 2
Sea Kale on the landward side of Cogden Beach – looking towards Portland

I’ve walked on the Cogden shingle many times and thought I knew it well, but today I was greeted by an extraordinary vision. Vast tracts of the stony beach bordering the land seemed, when viewed from a distance, to have been splashed with daubs of white paint. Upon closer inspection, I saw that these daubs were huge clumps of Sea Kale, some more than a metre across. The base of each clump comprised many thick, crinkly, grey-green leaves and the centre a prodigious display of flower stems topped with a froth of small white flowers so that each clump had more than a passing resemblance to an oversized cauliflower. By the time winter arrives, this riot of vegetation will have disappeared, leaving a sad scattering of brown leaves and stems but, under the pebbles, the crown will be waiting to produce next spring’s fantastic display.

Cogden Beach 1
Sea Kale flowers (and leaves)

Sea Kale has a long culinary history. The Victorians loved Sea Kale as a vegetable, particularly the young shoots which they forced by covering with pebbles. They picked it almost to extinction and, thanks to their efforts, it is now found only in a handful of places in the UK. There has been a recent resurgence of interest in Sea Kale, stimulated by celebrity chefs, but don’t be tempted to forage in the wild: Sea Kale is protected under the Wildlife and Countryside Act (1981) and anyway seeds and plants are available commercially.

Cogden Beach 3
Drifts of Thrift on Cogden Beach – with Sea Kale on the left of the picture.

 

Thrift at Cogden Beach
Flowers of Thrift (Sea Pink)

The dominant plant at Cogden in spring is Sea Kale, but it is by no means alone on the beach. Parts of the shingle are colonised by large drifts of pink Thrift, its flowers nodding merrily in a light breeze. I also saw Yellow Horned Poppies, just coming in to flower above their frizzy, silvery-green leaves. They will produce a succession of delicate lemon yellow blooms all summer and are named for their long, horn-like seed pods. There were a few clumps of Sea Campion covered with white trumpet-shaped flowers and some large mats of Sea Sandwort decorated with many small, starry, white blooms. The shingle garden is a profusion of flowers at this time of year but by the winter, there will be little to see and the beach will feel almost post-apocalyptic in its desolation.

Yellow Horned Poppy 1
Yellow Horned Poppy growing on the shingle at Cogden Beach

 

Yellow Horned Poppy 2
Close up of a Yellow Horned Poppy flower

 

Sea Campion at Cogden Beach
Sea Campion at Cogden Beach

 

Sea sandwort at Cogden
A dense mat of Sea Sandwort growing on the shingle at Cogden Beach

 

But how do these plants survive and prosper here? Cogden Beach is a harsh environment in all seasons with high winds, salt spray, occasional saline inundation and little or no soil or fresh water. Anyone who has stood on the pebble bank in a strong wind will know what I mean. If they managed to stay upright they will have tasted strong salt on the blustery air.

In fact, the plants are quite choosy about where they grow. The majority of beach plants at Cogden grow above the strandline on the sheltered landward side of the beach. Here there is an extensive tract of stable shingle stretching eastwards and the plants colonise this special environment. The plants that thrive here are also adapted to cope with harsh conditions. Frequently their leaves are fleshy with a waxy coating to prevent loss of water. The roots of some plants extend deeply in to the shingle in search of fresh water; in the case of Sea Kale they can stretch up to two metres. Some plants grow as large mats with extensive root systems to help them adhere in high winds. At the cellular level the plants have multiple mechanisms for dealing with the prevailing high salt.

But it’s not just the plant life that inspires people when they visit Cogden. Whenever I go there I find “beach art”, usually clever constructions made with the flat stones lying around the beach. This time I found a mini “Stonehenge” that must have taken hours to build.

Beach art at Cogden
“Beach Art”

 

 The featured image at the top of this post shows Sea Kale at Cogden looking west towards Golden Cap.  All the pictures were taken on May 26th 2015.  This article features in the July edition of the Marshwood Vale Magazine.

Cogden Beach is at the western end of Chesil Beach and can be accessed either via the South West Coast Path or from the National Trust Car Park on the coast road (B3157) between Burton Bradstock and Abbotsbury. OS grid reference SY 50401 88083, GPS coordinates 50.690271, -2.7035263.

National trust sign at Cogden

Coast path at Cogden

More solitary bees – and their unsavoury friends

cineraria nest in CP April 13
Andrena cineraria nests

 

On a sunny day just over a month ago, I was watching the solitary bees (Andrena flavipes) in a soil bank by the edge of one of the town centre car parks. It was a mid-April Sunday, the car park almost empty, so I wandered along the bank to check for any other bees living there. I had looked before and found nothing but this time I was surprised to find freshly disturbed friable soil and some bees about the same size as honeybees but with prominent black and white hairs. I took as many photos as their behaviour would allow and when I looked at various bee resources I reckoned these were most likely Andrena cineraria, the Ashy Mining Bee. The name refers to the colour of the hairs on the thorax of the bees and cineraria comes from the Latin for ashes.

Ashy Mining Bee 4
Andrena cineraria, can’t say if it’s male or female.

 

The Ashy Mining Bee is a very pretty solitary bee, particularly the female with her distinctive black and white hairs; the males are not so clearly marked although they do have white facial hairs. My photos  don’t allow me to identify males or females with any certainty although I did see two bees that were either fighting or mating.  I have not seen any females with pollen and I don’t think this is a large accumulation of nests but it does show that there are two species of solitary bee living in this unassuming soil bank in a town centre car park adjacent to the Leechwell Garden.

Ashy Mining Bee poss male
A. cineraria, probably male

 

Ashy Mining Bee 2
A.cineraria, probably male

 

Ashy Mining Bee Mating Pair
Fighting or mating?

 

While I was watching these bees, another large insect about the size of a medium bumblebee appeared and patrolled the nest area. With its smart coat of russet hairs and its long proboscis clearly visible, this was a bee fly, most likely Bombylius major.  These are parasites of A. cineraria and flick their eggs in to the soil nests where they develop and take over.

Bee fly
Bee fly

 

Later, I also noticed a smaller insect with a prominent yellow banded abdomen. In the photograph it is digging in the soil upside down. This is probably a nomad bee but, from this photo, I cannot say which species. A few days later I saw two Nomada flying about; these could be Nomada lathburiana known to parasitise nests of A. cineraria by laying eggs which develop and kill the bee egg or early larva.

seen near cineraria nest
Nomad bee digging near A.cineraria nest

 

Nomad bees
Two nomad bees flying near the A.cineraria nest region, possibly Nomada lathburiana.

 

Bees and neonicotinoids – another twist in the tale.

To the agrochemical companies and to many farmers they are essential tools ensuring efficient crop production. To environmentalists and to many bee scientists they are dangerous chemicals contributing to declining bee populations. I am talking, of course, about the neonicotinoid insecticides widely used in this country to control insect pests.

Last week two papers were published on-line in the journal Nature emphasising the dangers posed by these chemicals.

One paper, from a team at Newcastle University, investigated whether honeybees and bumblebees showed any preference (positive or negative) for food containing neonicotinoids; there had been suggestions that bees might avoid neonicotinoid-treated crops in the field. The new lab-based work showed that, when offered a choice, bees preferred to eat sucrose solution (nectar) containing neonicotinoids (imidacloprid or thiamethoxam) rather than control sucrose solution. If this occurs in the field then bees may forage preferentially on crops containing chemicals toxic to their health and inadvertently bring back these toxins to their nests.

The second paper, from scientists at Lund University in Sweden, showed that the neonicotinoid clothianidin, when used in the field, damaged wild bee (bumblebee and solitary bee) populations but was without effect on honeybees. I want to focus on this paper as it is the first controlled study of the effects of a neonicotinoid on honeybees, bumblebees and solitary bees under field conditions. Let’s start by looking at the background.

Three years is a long time in science

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Back in 2012, two studies were published showing that neonicotinoids, even when they didn’t kill bees, could affect bee behaviour in a way that impaired survival of honeybee and bumblebee colonies. The findings showed that these chemicals could contribute to a decline in the numbers of bees and other pollinators. These observations had a big effect on policy and indirectly contributed to the current partial ban on the use of three neonicotinoids in Europe.

One of the papers was from Dave Goulson’s lab, then at Stirling, and found that even at the low doses typically encountered on treated crops in the field, neonicotinoids substantially reduced the number of queens produced by bumblebee colonies, so impairing survival. In Goulson’s study, bumblebees were treated with neonicotinoids in the lab before being allowed to fly freely. This is called a semi-field design and some have suggested that the findings cannot be extrapolated to the real world. The levels of neonicotinoids have also been criticised although these were very carefully thought through.

There was considerable media interest in this work, nicely described in Goulson’s latest book (A Buzz in the Meadow) and the UK Food and Environment Agency (FERA) labs in York hastily set up a preliminary field trial to examine the problem. During the spring and summer of 2012 they studied three fields of oil seed rape, one treated with the neonicotinoid, imidacloprid, another treated with the neonicotinoid, clothianidin and a third untreated field to act as a control. Bumblebee (Bombus terrestris) nests were placed by each field and the occupants were left to fly freely and build their colonies. Extensive analyses were performed including colony growth, the pollen collected by the bees and pesticide residues detected in pollen and nectar.

Superficially this sounds like a rigorous study (free flying bees, compare neonicotinoid-treated with control, plenty of analyses and so on) and it should have given an indication of the effect of neonicotinoids under real-world field conditions. The success of the trial depended on the bees foraging on the crop near their nests so there should have been clothianidin-exposed colonies, imidacloprid-exposed colonies and neonicotinoid-free controls. Unfortunately the bees had other ideas; they largely ignored the flowering oil seed rape by their nests, foraging further away and returning with pollen from crops treated with another neonicotinoid, thiamethoxam. This completely negated the original design so that, in my view, no valid conclusions can be drawn from the study, despite official pronouncements.

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The new Swedish study

The FERA work was a valiant but flawed attempt to study the effects of neonicotinoids on bumblebees under field conditions and it was clear that a properly conceived field trial was required. The ambitious new study from Lund University mostly fills that void.

The Lund team selected 16 landscapes surrounding spring-sown oil seed rape fields in different parts of southern Sweden in 2013. The landscapes were divided in to 8 pairs on the basis of the nature of the surrounding countryside and for each pair one was sown with seed treated with the neonicotinoid, clothianidin and the other was sown without neonicotinoid, to act as a control. All seed also contained a fungicide. The neonicotinoid-treated seed also contained a pyrethroid to protect plant roots but there was no evidence that the bees came in to contact with this chemical.

Honeybee hives, bumblebee (Bombus terrestris) colonies and solitary bee (Osmia bicornis) cocoons were placed by each field during the flowering season and their progress was followed. Additionally, the numbers of free flying wild bees (bumblebee and solitary bee) were assessed at each field during the flowering season. Pollen brought back by bees was analysed for flower type and for pesticide residues. The study was large enough to allow statistical analyses to be performed so that valid conclusions could be drawn although the design was unable to detect effects smaller than 20%.

Unlike the FERA study, bees did forage on the oil seed rape adjacent to their colony based on pollen analysis, although this was not an exclusive choice. Bees near treated fields brought back pollen and nectar containing clothianidin whereas those near untreated fields did not. The study design seemed to have been successful and the results were clear:

1. Honeybee hives behaved similarly by treated and untreated fields; there was no effect of the pesticide on colony strength. This is good news for honeybees and for beekeepers and agrees with a 2014 field study from Canada also using clothianidin.

2. Bumblebee colony growth and reproduction were reduced near treated fields. This agrees with earlier semi-field studies so that it is now difficult to avoid the conclusion that agricultural use of neonicotinoids has damaging effects on bumblebees.

3. Whereas solitary bees placed by untreated fields emerged from cocoons and built new nests, this did not occur for cocoons situated near treated fields, possibly because of navigational problems caused by insecticide exposure.

4. The number of free-flying wild bees was reduced by about 50% at the treated fields.

The implications of the new Swedish study

Honeybees were not affected by foraging from a neonicotinoid-treated crop whereas wild bees (bumblebees and solitary bees) suffered reductions in numbers and reproductive ability. Wild bees are, therefore, more sensitive to neonicotinoids than honeybees. This may be because, as James Cresswell at Exeter has shown, honeybees break down neonicotinoids more quickly than bumblebees so that honeybees experience lower doses.

The effect of the neonicotinoid on wild bees is an important result for several reasons. Wild bees are important pollinators, contributing more than half of the “pollination service” required for crops. Crop yield and quality will suffer if these insects are lost so we need to look after them and that may need to include rethinking use of pesticides.

The differential sensitivity of bee types to neonicotinoids shows that environmental risk assessment of new and existing insecticides, typically performed in short term lethal studies on honeybees, is inadequate to determine long term effects on different bee types in the field.

These new data will add to the pressure to extend the European moratorium on the use of three neonicotinoids as seed dressings after the initial two year period ends in December. There is, however, concern that if neonicotinoids are not available then farmers will use older insecticides that may be more dangerous for bees. Perhaps farmers should rethink their use of pesticides and return to a “treat when required” policy rather than using neonicotinoids prophylactically.

When the three neonicotinoids were temporarily banned in 2013, farmers claimed that the yields of crops would be drastically reduced. It is interesting that in the first season when crops were grown from untreated seed in the EU, the yields actually increased. Perhaps we should rethink the use of chemicals more generally in modern farming.

I know a bank where the wild bee goes

The young woman sitting in her car rolled the window down and enquired: “Would you mind telling me what you are doing?” I was in one of the town centre car parks adjacent to the Leechwell Garden and had been peering at a bank covered with scrappy grass and flowers, occasionally taking photographs. She continued hesitantly, asking if perhaps I was interested in the wild flowers. She was right, of course, but that was only part of the story.

The car park is called the Nursery, its incongruous name purloining a bit of local history. Difficult as it is to believe,  until the early 1980s this part of central Totnes housed several fine commercial market gardens.  All kinds of vegetables were produced in season and sold through shops in the town. The land that now forms the Nursery car park used to be covered with greenhouses growing tomatoes, lettuces and out of season chrysanthemums.

car park sign
The soil bank by the car park on a quiet day

I find it sad that these very productive market gardens were tarmacked over to provide car parking but that is what happened. Narrow banks of soil were left around the parking area, perhaps to leaven the bleakness. Some of these banks are now covered with brambles, others with grass. The bank I have been watching is about ten feet wide and south facing. It is mostly covered with grass although there are a few exposed areas of friable soil; at this time of year there is a good population of flowering dandelions and celandines. Behind the bank is a high wall clad in ivy and on sunny days, the area gets quite warm attracting many insects.

Solitary bee on daisy
One of the small bees feeding on a daisy

 

solitary bee March 26
Another of the small bees

 

Last year, my friend Susan Taylor told me about some solitary mining bees living in this bank. I had a look, but didn’t study them properly, mostly owing to my ignorance. This year I decided to try to identify the inhabitants and occasionally popped in to the car park to see if anything was happening. It wasn’t until the third week of March that I was rewarded with my first sighting of the solitary bees. On a warm, sunny day I found a cloud of small, slender bees, each about two thirds the size of a honeybee. They were flying about in an excited, staccato manner about twelve inches above the ground repeatedly changing direction, occasionally bumping in to one another, occasionally stopping to feed from dandelions. Susan Taylor describes this behaviour as their “Sun Dance” and they do seem to fly only when it is warm and sunny. From my photographs, I could see their black abdomen with prominent white stripes and their thorax and face decorated with pale brown hairs.

Solitary bee female April 6
One of the larger bees showing the orange-yellow hairs on its back legs

 

nest area
The nest area with tunnels built in friable soil

 

Solitary bee females April 6 2
Two of the larger bees crawling about

 

The “Sun Dance” continued on warm days and then about two weeks after I first saw the small bees I came across an area of friable soil in the bank with some prominent holes which I assume are the nests. Here I saw a few larger bees that were otherwise quite similar in appearance to the “Sun Dancers”. There was one clear difference apart from size and that was the orange-yellow hair on their upper back legs. They were also behaving quite differently, crawling around near the holes but rarely entering. I didn’t see any evidence of mating but a few days later I began to see some of these larger bees returning to the holes loaded with chrome-yellow pollen and quickly disappearing inside to equip their nests. On good days, the smaller bees were still evident but in gradually decreasing numbers. The larger bees have continued to collect pollen; the dandelions are declining but many local fruit trees are now blossom-covered so there is no shortage.

solitary bee female with pollen April 12
One of the larger bees with pollen

 

So, what have I been seeing? I have compared photographs of my car park-bees with pictures in bee books and with the many photographs of solitary bees on the internet. It is very difficult to make a firm identification, but I will offer a suggestion. The smaller bees are likely to be males and the larger bees the females of the same species. What we have called the “Sun Dance” is a crowd of males waiting for the females and getting over-excited, rather like sulky adolescent boys. I did not witness mating but collection of pollen and nest building are performed only by mated females. Their early emergence, their nest location, the complete white bands and the orange-yellow leg-hairs on females but not males suggest Andrena flavipes, the Yellow-legged Mining Bee. These are common mining bees that build nests in tunnels in soil banks. They are found in the southern UK and may have a second brood in mid-summer; I shall have to keep watch.

It would be interesting to hear what others think about this tentative identification.

………………………………………..

But why am I interested in these bees if they are not rare? Why am I taking the trouble to watch them and take photographs?

I believe it is important to document these creatures, to get to know their life cycles and spread the word. Their emergence and nest-building each spring is one of nature’s amazing phenomena and I feel privileged to watch. These bees are also important pollinators; it’s good to know they are around and we should aim to support them.

I find it fascinating that these small lives are being lived in a busy town centre car park, literally under our noses. Perhaps realising that there is life in the soil banks makes up in part for the loss of the market gardens?

I explained some of this to the young woman in the car and she seemed interested, if a little bemused. It’s not every day you stop in a car park and get an enthusiastic lecture on solitary bees!

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