A rare discovery - winter active bumblebee nest

Most bumblebee queens hibernate during the winter however towards the end of the 1990's a few winter sightings of Buff-tailed bumblebees (Bombus terrestris) workers were recorded. Winter colonies had previously been known from New Zealand where the species had been imported.

The buff-tailed bumblebee is our most common species but even so winter activity is only known at a few locations in the UK. From the distribution of records the availability of winter flowering plants seems as important as climate if not more so - none have been recorded further north than Hull*.

With few sightings there is still much to be discovered about these winter colonies. For example it is not known how many colonies that produce workers in December and January successfully complete their life cycle - see earlier post, Missing male bumblebees - a mystery?

Although I have been observing Buff-tailed bumblebees in Falmouth for the last three winters the odds of finding a nest were slim. In the end it turned out to a mixture of luck meeting a prepared mind. I sort of stumbled upon it but knew immediately what I had found.

How rare a find is it? To my knowledge the earliest winter nest (December through to February) was discovered in London last December and that is still active to date**. Brigit Strawbridge observed new queens carry pollen back to their old nest in late November 2011 but no males were seen. This was a very late nest to be active, not typical behaviour and possibly a second generation brood. See my post, Bumblebees - A Winter's Tale for more information on second generations. There is also the possibility that the new queens may have founded nests themselves rather than hibernate.

There is still much to learn about this winter activity and it is possibly variable from location to location and year to year. People continue to see winter active workers such as Philip Strange, who has seen them in Paignton for the second winter running.***

Even though the video above is an edited highlights of arrivals and departures it is clear this nest has been established for some time. How long would be a guess but possibly it might be the nest of the workers I began observing in December.

In the video you can see the bees are bringing back different coloured pollen this shows that they are visiting different species of flowers. From the data I collected while filming and intend to collect on my next visit it should be possible to estimate of the size of the colony.

It will be interesting to see how long the colony remains active, current thoughts are that it will reach its end soon but I am keeping an open mind. Towards its end new queens are produced and as they often return to the nest they will hopefully be easier to observe. Males unfortunately leave never to return, indeed recent research suggests they do not remember the location of their nest. I am going to need a bit more luck to spot them.


* See BWARS 2010 infosheet here Click

** Literally a hour after posting the blog I read that the colony was still active (there had been no news of it since December) and have revised this post.

***Read Philip's blog for details of the winter active bumblebees in Paignton.      Click Here

  

Falmouth Cemetery: a haven for wildlife

Possibly the last population in Cornwall of the Red-girdled

Mining bee lives and nests in Falmouth cemetery.

When I discovered the old parts of Falmouth cemetery on a casual walk in 2014 I had no idea of its importance as a sanctuary for wildlife. It was clear that there had been minimal maintenance for quite some time. The County Council was responsible for the general upkeep but maintenance of the graves and monuments was the responsibility of the family. Clearly many had been left by the families to go back to Nature. As a result Falmouth had been left a legacy that contained a wide variety of wildlife.

The small copper butterfly has declined by 75% in urban

locations between 1995 - 2014. Another important

species found in the cemetery.

For the past two years I have been recording the species of wild bees to be found in the cemetery. While some species can be found elsewhere in Falmouth the scarcer ones seem limited to both living and nesting in the cemetery. Many solitary bees species only forage short distances from their nests, usually a distance of about 50-200 meters depending on the size of each species. So far I have discovered 37 species of solitary bees within the cemetery, some are rare or scare both nationally and in Cornwall.

Newly emerged Queen Red-tailed bumblebee. Raised in a nest
in Falmouth cemetery she visited nearby flowers to build her
reserves before hibernating

The key element why the old parts of the cemetery is able to support such a rich variety of wildlife are the range of wildflowers that grow in the cemetery. From early spring to late autumn they provide both nectar and pollen. The fact that the ground is largely undisturbed also benefits ground nesting species such as most bumblebees. 

The value of these parts of the cemetery to both wildlife and the local community is clearly something to be safeguarded. For this reason I have written the document you can download below. It is a guide to some of the species that can be found there together with an overview of the ecology. 

Click to Download PDF

  

While compiling my records for the old parts of the cemetery responsibility for its maintenance passed from Cornwall County Council to Falmouth Town Council. This brought about substantial changes in the way in the way the cemetery is managed. As a response I included a section on maintenance and its importance in ensuring the conservation of the wildlife in the cemetery. Having received a reply from the town council to an earlier draft I have now revised the maintenance section to reflect this.

It is my hope that this will open a debate on how best to manage the cemetery. The maintenance changes are significantly changing both the character of the old parts of the cemetery and its value to wildlife. The degree to which these are desirable are open to discussion. It is important that as many voices as possible are heard in deciding its future.

The current document should be seen as an introduction to the cemetery's biodiversity. During this year I hope to be adding more records to the list of species. I also hope to build a better picture of its butterfly species and also include hoverflies. As its flora plays such a vital part in its ecology I hope to build a seasonal list of its wildflowers. This blog will keep you up to date with my progress.

If you have any photos of wildlife in Falmouth that you would like to share you can be post them on the Falmouth Nature Facebook page or to Twitter including @FalmouthNature.

Click to visit Facebook Page

Falmouth buzzes in January

January is the first full month of winter yet with its mild climate Falmouth still buzzes. Loudest of the insects to be heard are the buff-tailed bumblebees on their constant search for pollen. On two days this month I watched workers foraging until ten minutes before sunset. An indication that their nest lies in a garden somewhere within the town.Honeybees are not so tolerant of cold weather and only ventured out on mild days in January.

Honeybee visiting camellia flower

Throughout the winter it is usually possible to see two species of hoverfly on all but the most coldest of days. The marmalade hoverfly (Episyrphus balteatus) and Meliscaeva auricollis. They can often be found visiting Mahonia flowers in Fox Rosehill Gardens. Another hoverfly that can occasionally be seen on milder winter days is Eristalis tenax or drone fly - it resembles a honeybee and can even buzz like one. 

Marmalade hoverfly (Episyrphus balteatus)

Meliscaeva auricollis

Eristalis tenax

Sunny days can tempt Red Admiral (Vanessa atalanta) butterflies out of hibernation either to visit flowers for nectar or simply to sunbath.

Red Admiral (Vanessa atalanta)

Other insects to be seen on mild days are the flies, Calliphora vicinia and Scathophaga furcata. 

Calliphora vicinia

Scathophaga furcata

January Wildflowers

Frost still lingered in shaded areas of

Falmouth cemetery

This was the second year I participated in the Botanical Society of Britain and Ireland’s New Year Plant. My chosen day was Tuesday, 3^rd January and inauspiciously it began with a frost that lingered in shaded areas all day. The location was the old parts of Falmouth cemetery.

Primrose

Primroses can begin to flower quite early in Falmouth, a few can be seen as early as October in a mild autumn. Winter Heliotrope usually starts to flower in December and peaks in January.

Winter Heliotrope flowers possess a vanilla scent

An important source of pollen and nectar is the often maligned dandelion (above), there appeared to be less than usual about this year. Ivy-leafed toadflax (below) is a low growing plant that often grows on stone walls.

Ivy Flowers

Ivy begins to flower towards the end of August with its main period being September and October. A few flower heads were still to be seen in January.

Daises

Red Campion

Daises and red campion are both wildflowers that can be found in most months of the year. The biggest surprise of the month was discovering a single flower of Trailing Tormentil.

Trailing Tormentil flower in January

On the coastal path gorse was in flower.

Gorse

Bumblebees - A Winter's Tale

Nature loves variation; evolution can be thought of as playing, let’s try something different and see if it works. Not only has this produced an astonishing variety of species it also results in variations within specie. Nature plays dice and making general statements is often a bit of a gamble. Quite often there are exceptions that complicate matters.

The bumblebee is a good example of this for while most have a life cycle of one generation in a year there are exceptions. Generally new queens emerge in late summer, they will mate and then forage for food to build up their reserves before digging a burrow that they hibernate in.

Upon emerging the queens feed on nectar while their ovaries mature and then begin to search for a suitable nesting site. Once she has established a nest she will lay the first batch of eggs to produce female workers. Bees can determine the sex of their eggs as fertilised eggs produce females and non-fertilised eggs males. The queens sit on their eggs and it is thought that temperature can influence the size of the workers. Warmer eggs producing larger larvae. The amount of food they consume is also likely to determine their adult size.

The queens forage for nectar and pollen to take back to the nest for their larvae to feed on. The larvae eventually spin a cocoon from which they will emerge as adult worker bees. Once enough workers have been produced to bring an adequate amount of pollen and nectar back to nest the Queen no longer leaves it.

 

Eventually the point is reached where the queen starts to lay male eggs and females to become queens not workers. Up to this point the queen has been releasing pheromones to suppress the female workers from becoming fertile and laying their own eggs. As she now wants to produce eggs that will develop into fertile queens she ceases to produce the phoromones. Without them the social order of the nest breaks down and some of the workers will attempt to lay their own unfertilised eggs to produce males. In many cases the unrest within the nest will lead to the workers stinging the queen to death.

The adult males leave the nest in search of queens to mate with. With their own nest in a state of turmoil they are homeless and fend for themselves. If on a rainy late summer’s day you see a wet bedraggled bee it is likely to be a male. In their search for newly emerged queens from other colonies they can travel up to 10km from their original nest.

This brings us back to where we started and the general life cycle of a bumblebee colony is completed - now for some exceptions.

Let us start with the Early Bumblebee (Bombus pratorum) as in this country there is geographical divide in the behaviour of queens. In the North pratorum follows the life outlined above. In the South though some of the new queens produced in a year rather than hibernate will establish nests to produce a second generation in the same year. It would be easy to assume that the difference is due to the climate. That spring arrives earlier in the South and frosts later. It sounds sensible but some bumblebees in Norway challenge that idea.

The Hearth Bumblebee (Bombus jonellus) is found both in this country and Norway. In this country like Bombus pratorum in the south it can produce two generations in a year and the same is true in Norway. Not only that but the subspecies, Bombus jonellus sub borealis occasionally produces two generations in Troms county, Norway that is north of the Artic Circle. Length of season does not of itself seem to be determining whether a queen produces a second generation or hibernates.

In the U.S.A. it seems three species in Oregon can produce a second generation in a single year. These are the yellow faced bumblebee (Bombus vosnesenskii), the fuzzy-horned bumblebee (Bombus mixtus) and the black-tailed bumble (Bombus melanopygus).

Studies in Norway and the U.S.A. suggest mild and dry summer that result in an abundance of suitable flowers species in late summer is a key factor in motivating some bumblebee species to produce a second generation.

Winter active bumblebees are another exception to the general behaviour of bees in this country. These are queens who establish a colony with workers that are foraging through the winter months. For several years winter active Buff tailed Bumblebees (Bombus terrestris) colonies have been recorded mostly in southern urban locations but with outliers as far north as Hull. In locations where this occurs it seems to become a regular occurrence. This is the third year where I have recorded winter active terrestris in Falmouth. This year for the fist time I also found Garden Bumblebee (Bombus hortorum) workers on the same Mahonia flowers as terrestris workers. This mirrors evidence from New Zealand where we exported both species in the 19th Century. There terrestris is the most common winter active species with hortorum less frequently seen. Another exported species Bombus ruderatus has also been recorded as being winter active there, it will be interesting to see if this eventually happens in this country.

It is not known what prompts a new queen to hibernate. Most enter hibernation before the arrival of cold weather, so temperature appears not to be a trigger. It may be that once a queen has built up her reserve being in a burrow is the safest place for her. Combining the time spent in their hibernation burrow with that spent in their nest suggests that queens have a preference not to be out in the open. Most of a queen’s life is spent sheltered and protected.

Generally the instinct to hibernate after mating and building up their reserves is strong in queens of all species. As the exceptions show the strength of the instinct is variable in at least a few species. Going against the norm is a gamble. For example a queen that begins a colony in the late autumn will be reliant on the availability of flowering plants throughout the winter. In the right urban location the odds of survival are favourable elsewhere they are bleaker. 

Another potential problem faced by a bumblebee colony that breaks the widespread timings of their species' lifecycle is finding mates for their males and queens when most of their species are unavailable. A small isolated population can be susceptible to inbreeding.

Variability within a species offers the possibility of adapting to change and taking advantage of new opportunities. If all of life is a gamble then spreading your bets is the safest option.