Falkirk’s forward-looking green progress

Pollinator-friendly actions are nothing new to Falkirk Council.  Over the years they have been involved in a range of projects which have made life easier for pollinators, and brought considerable enjoyment to people.

So what have they been up to lately?  We caught up with Anna Perks, a local biodiversity officer, to find out.

“I think one of our most exciting local developments has been that Falkirk Council has commissioned consultants to carry out a piece of work looking at the potential for habitat creation on our land/buildings to help sequester CO2.  Although CO2 sequestration is our primary goal, we anticipate that many of the identified opportunities will also have benefits for pollinators and other biodiversity. 

“To deliver this project we will be looking at a range of habitat creation opportunities, including woodland, long grassland, wetland, and green/brown roofs and walls.”

Other bodies liaise with Falkirk Council to good effect in projects which, in passing, improve prospects for pollinators.  Take, for example, the work of amphibian and reptile specialists Froglife.  As part of their ‘Come Forth for Wildlife’ project they created a number of small meadow strips in four of Falkirk’s parks. That was great news in its own right, but in late 2020 volunteers carried out a bit of supplementary sowing at those meadows.  It’s a classic example of where helping one element of biodiversity can have a positive knock-on effect for another group.

Anna has developed a keen eye for new ideas or practices and relays these to her colleagues where there is a potential biodiversity gain. 

“I have written a report detailing proposed changes to Falkirk Council’s grass and verge cutting regimes”, she explains by way of example.  “This could not only benefit biodiversity but meet other objectives such as our aims to take action to combat climate change, and deliver budget savings.  I have just had approval from the Council to  implement a pilot phase of these changes this year (at  35 sites) and review these in spring 2022 with a view to wider roll out after that.”

Anna is realistic that change doesn’t always happen overnight. However,  approval to run this pilot represents significant progress, It’s an excellent sign of the direction things are headed.

This forward thinking is nothing new in a council area which saw pollinator-friendly planting in a range of parks in spring 2018, and native bulbs planting in autumn 2018 to complement those new meadows. This tied in well with Buglife Scotland’s B-lines initiative and engaged several local groups with pollinator activities.  Working with groups such as Buglife Scotland has been a welcome element of Falkirk’s approach.

And the progress on ‘completed’ sites continues with the council recently purchasing equipment that allows them to cut and lift long grass – a key element to building on the good initial planting work. This will prevent soil becoming too nutrient-rich and favour wild flowers. 

It’s intriguing to see how Falkirk has built on its early actions to continue to make solid environmental improvements. Come spring and summer the community here will be able to enjoy a host of pollinator friendly flowers. And that’s great news for pollinators – and people.

Blistering brigands

By Athayde Tonhasca

Flying over coastal dunes in the American state of Oregon, a male silver digger bee (Habropoda miserabilis) picks up the scent of a female. The smell takes him to a dark shape hanging from a twig: he zeroes in for a romantic encounter before she has time to flee. But as he touches the female-to-be, the object breaks up into a mass of louse-like creatures who in no time crawl onto him, clinging on for dear life. These hitchhikers are planidia (singular planidium, from the Greek planis, meaning ‘wanderer’), which are a type of larva that don’t look at all like larvae. They have well developed legs, are quite nimble, and they’re phoretic, that is, they use another organism to be transported to a new location. 

The puzzled male bee moves on carrying his passengers, and eventually finds a real female. During their encounter, the planidia jump ship again and attach to the female bee. She will then carry the uninvited guests to her nest, where their joyride ends and their parasitic nature is revealed. They start eating the bees’ pollen stores, eggs and larvae before moulting into ordinary, grub-like larvae, which carry on depleting the bee’s provisions and offspring. The larvae go through several stages, and in the following spring emerge from the host’s nest as adult blister beetles of the species Meloe franciscanus.

Aggregations of Meloe franciscanus planidia on grass stems and on the dorsal surface of a male silver digger bee © Saul-Gershenz et al. 2018. Proceedings of the National Academy of Sciences 115(39) 9756-9760; DOI: 10.1073/pnas.1718682115.

The tale started with a sophisticated deception: the planidia lured the male bee with chemical signals that mimic the host’s sex pheromones. But the trickery goes further: another population from the Mojave Desert (California) produces different chemicals to attract another species of bee. Not only that, the planidia match their perching heights with the height at which local male bees normally patrol for females.

The cunning behaviour of M. franciscanus is just one of the distinctive facts about blister beetles (family Meloidae). They undergo hypermetamorphosis, by which one of their larval stages is radically different from the others: planidia don’t look or behave at all like other immature phases. Females are prodigiously fecund, sometimes laying several thousand eggs. This reproductive potential possibly evolved to counterbalance high mortality: planidia will climb onto any insect they can reach, so the risk of picking the wrong host is considerable.

Blister beetles are also known as oil beetles, as many species exude drops of oily haemolymph from their joints when alarmed or disturbed. This liquid contains cantharidin, a toxic and irritating chemical. Apothecaries of ancient times used dried and ground up oil beetles as a blistering agent to remove warts and moles. One species, Lytta vesicatoria, is the source of a concoction named Spanish fly, the usage of which is not appropriate for discussion in a family-orientated blog. Medicinal and aphrodisiacal uses of blister beetles are unsubstantiated and risky to say the least, as cantharidin is about as toxic to humans as cyanide and strychnine. And there’s no known antidote. Remarkably, dozens of insect species, including some biting midges, feed on this oil beetle exudate, presumably to acquire its defensive properties.  

There are five species Meloe oil beetle in Britain, but only two are common: the black (M. proscarabaeus) and violet (M. violaceus) oil beetles. Adults feed mostly on flower parts, pollen and nectar. They are most often seen between March and July on open soil, as they search for a mate or a site for oviposition. Our oil beetles are all parasites of solitary bees, but we don’t know whether they use similar ruses to their American cousin: they probably do.  

A violet oil beetle. Note the drop of haemolymph on its thorax.  ©Darkone, Wikipedia Creative Commons

Many people can’t warm to parasitic insects, especially when their victims are lovable bees. This attitude is prejudiced and ill-informed: parasitic insects are important components of ecological communities by regulating population sizes, with profound effects on food webs and biodiversity. Oil beetles’ life histories are magnificent examples of adaptation and survival skills. And they need our care as well: some of our species are declining. 

Solitary bees have many natural enemies, and oil beetles are one of the main factors of brood mortality for those species that nest on the ground such as Andrena spp. mining bees. Despite this, it is estimated that less than 20% of their brood is lost to natural enemies. Bees may be facing several environmental challenges, but oil beetles are not one of them. Bees and beetles can be both valued, admired and protected. 

Violet oil beetle planidia. ©Natural History Museum, http://data.nhm.ac.uk/dataset/collection-specimens

Tayside triumph

How appropriate that the third Keep Scotland Beautiful ‘It’s Your Neighbourhood’ pollinator award was won by Bonnie Dundee.  2020 was also the third year of Bonnie Dundee’s focus on pollinators, and they delivered an extraordinary effort in what, by any standards, proved an unprecedented year.

The volunteers from the It’s Your Neighbourhood Bonnie Dundee group design and maintain attractive planting in Dundee city centre to encourage insects and improve the wellbeing of workers, residents and people visiting the city.

Working closely with Dundee City Council, the group plant with pollinators in mind, and to educate and increase people’s awareness and understanding via notices, contact with schools and nurseries and through online communications. The volunteers are responsible for fourteen planters on Union Street, four in Westport, fourteen outside the square at Dundee Science Centre plus an Urban Orchard of eight heritage trees in fourteen planters, a raised herb area and seven flower beds in the William Gardiner Square at the back of the Overgate shopping centre and an area of Slessor Gardens.

Dundee’s enthusiastic volunteers deliver a wide range of activities each year, including tending planters, community gardening, litter-picks, encouraging biodiversity and helping to improve local parks.

For the past three years they have been doing all of the above with an emphasis on ensuring pollinators are catered for. 

Catherine Lawson explains the thinking behind the group’s actions.  “We have been planting with pollinators in mind for some time now,” she notes, “educating and increasing the public’s awareness and understanding through notices and online, plus encouraging everyone to sow seeds. 

“The city centre areas we maintain have included attractive pollinator-friendly planting, such as our planters on Union Street where we planted varieties of Rudbeckia, and our garden at Slessor Gardens which also included Tithonia Torch and Echium Blue Bedder. The Thyme and Hyssop in our community herb-beds were bee magnets when in flower, and our cosmos was loved by hoverflies! 

“In 2020 we hoped to build on the success of our 2019 pollinator identification notices and pollinator walk, but had to hold back due to Covid-19. Instead, we teamed up with ‘Seeds of Hope Scotland’ and handed out 95 packets of Scottish wildflower seeds during lockdown to individuals and groups throughout Dundee. 

“Communication was done electronically, and seeds posted out to maintain social distancing. We highlighted the importance of pollinators, and the fact that absolutely everyone can be pollinator friendly, even if they only have a window box. “

This approach overcame what threated to be a significant hurdle. The response was really positive, with participants sending on celebratory photos of their seed patch to the Bonnie Dundee organisers.  There is something enduring and uplifting about planting, and the rewards of blooms are both a personal and shared delight.

Through the increased communications and seed-packet sharing a sense of community was fostered, despite the restrictions, and individuals, some of whom felt isolated, welcomed being part of a city-wide project. As the seasons progressed everyone involved enjoyed watching their seeds grow and bloom, and loved seeing the visiting range of insects particularly the bees and butterflies.

As we increasingly come to recognise the positive link between nature and our health this collaborative approach paid dividends in the City of Discovery. The attractive planting in Dundee city centre not only encouraged insects but clearly had the ability to cheer people and engage them with a key biodiversity issue.

The group harnessed social media to keep their project ticking over with ease. They entered a video of the project into the Dundee Flower & Food Festival’s Virtual Show and uploaded it to their popular Facebook page (@BonnieDundeeBloom). 

Grasping technology in this way quickly highlights positive actions and the long term pollinator-friendly planting message Bonnie Dundee were keen to see circulated. Along the way this attractive messaging demonstrates the importance of pollinators to our economy and enjoyment of the outdoors.

This is the third year that NatureScot has supported this pollinator-friendly award. The number of entrants increased again, and the variety of successful pollinator-friendly approaches was clear in all the entries.

But anyone hoping to wrest away Bonnie Dundee’s crown next year will have to work hard. The Taysiders don’t intend to rest on their laurels.  As Catherine explains “We plan to use the prize money to buy more Scottish seeds, from ‘Seeds of Hope’ and perennial seeds from Scotia Seeds to distribute with instructions to individuals and groups so we spread knowledge even further.”

Keep Scotland Beautiful CEO, Barry Fisher was quick to praise the Dundee project and the commitment that lies behind it. “We know that lockdown resulted in many people reconnecting with nature and biodiversity in their local neighbourhoods,” he noted. “This can only be good news for our environment, locally and globally, as people’s renewed appreciation and reconnection will ultimately help us tackle climate change and protect our planet.   

“I’d like to thank Bonnie Dundee for the efforts its volunteers have made to keep Dundee beautiful this year, for its people and nature, and look forward to seeing how the work blooms with the prize money.”  

Being positive in a time characterised by lockdowns and restrictions can’t have been easy. But as the It’s your Neighbourhood gathering continually demonstrates, Scotland is blessed with some remarkably determined and resilient community groups.

Smorgasbord or Spartan: the consequences of pollen diets

By Athayde Tonhasca

There is nothing visibly remarkable about the mining bee Andrena florea. This bee, one of the 67 Andrena species in Britain, is found in open scrubby areas, grassland and woodland edges of south-east England. But one thing makes this bee unusual; it only takes pollen from white bryony (Bryonia dioica).

Andrena florea, which is commonly and unsurprisingly called the white bryony mining bee, is a rare British example of a bee that forages on a single plant species. This dietary restriction is circumstantial, because white bryony is the only plant of this group occurring in Britain. In continental Europe, A. florea has other Bryonia species available. So in a wider geographical context, this bee is oligolectic (or an oligolege) that is, it collects pollen from a few related plant species (from the Greek oligo: few, scant; and lect: chosen, picked).

A white bryony mining bee and its pollen source, white bryony © Aiwok (L) and H. Zell (R), Wikipedia Creative Commons

Pollen specialisation can be a considerable drawback for a bee because food may be scarce even in a landscape full of flowers, and this may limit populations of some species. For example, until recently the white bryony mining bee was rare and threatened in Poland. This has changed with the spread of white bryony into the country’s urban areas. And yet, a considerable number of species are pollen specialists; in some habitats, they make up the majority of the bee fauna. So pollen specialisation must have its advantages, for example by allowing more efficient flower visitation and pollination rates, which benefits bees and plants.

Polylectic bees are at the other end of the spectrum: they collect pollen from various unrelated kinds of flowers. The advantages of being a pollen generalist seem evident: there is more food to choose from and it’s available for longer, as flowers blossom at different times. But these bees must also have an array of physiological adaptations to overcome a variety of chemical and physical barriers to different types of pollen. This could be too costly for a bee’s metabolism.

Pollen is a rich source of protein, lipids, vitamins and minerals. But it also contains secondary compounds that may be noxious to some bees, and pollen grains are often protected by indigestible coating. These barriers explain why few insect taxa rely on pollen alone for food, and could also explain why most polyleges (polylectic bees) exhibit a degree of pollen specialisation: for example, heather (family Ericaceae) and legumes (family Fabaceae) make up over 70% of the pollen collected by British bumble bees, despite local abundance of other pollen sources.

Experiments with the closely related red mason bee (Osmia bicornis) and horned mason bee (Osmia cornuta) show the effects of different types of pollen. Red mason bee larvae develop well on buttercup pollen (genus Ranunculus), but fail to do so on pollen from viper’s bugloss and related plants (genus Echium); the reverse happens for the horned mason bee. Both bees do well on field mustard pollen (genus Sinapis), while neither develop on pollen from tansies and related species (genus Tanacetum). But the story is a bit more complex: neither bee shows any negative effect as long as they are not restricted to ‘bad’ pollen. In fact, unsuitable pollen is part of the bees’ natural diet. Other bee species show similar patterns.

Viper’s bugloss (1), creeping buttercup (2), field mustard (3) and tansy (4): nutritious/poisonous food for the right/wrong bee. © Wikipedia Creative Commons

So what can we conclude from all this?

Oligolecty and polylecty are both successful evolutionary strategies. Some bees depend on a few plants, others have diversified pollen diets. The range of hosts can be narrow or wide, depending on the species, but setting aside a handful of exceptions, bees need pollen from different plants to complement nutritional imbalances or to mitigate the effects of harmful secondary metabolites. But even pollen of low nutritional quality or digestibility is taken, as long as it’s a portion of a balanced diet.

These aspects have important consequences for the conservation of bees. They need a diversity of flowers, and plenty of them. Habitats such as semi-natural grassland, hedgerows, field borders, cover crops, brown sites, road verges, wild gardens and weedy parks are all suitable. Planting is helpful, but except for the honey bee and some bumble bees, we know little about what plant species to use. The safest action is to let our wild plants go wild, so that we have bigger, and more diverse flower-rich habitats. That’s not much or too difficult a task to assure the future of our most important pollinators.  

The not so sweet side of honey bees

By Athayde Tonhasca

Our honey bee – more precisely, the Western or European honey bee, Apis mellifera – is the world’s most important crop pollinator. Thanks to an ancient history of domestication, farmers can count on a work force of up to 60,000 bees per hive, which can be managed and moved from place to place to pollinate flowers of many shapes and sizes. Unlike the vast majority of bee species, honey bees live in highly social, organised colonies that last for many years. They fly long distances in search of food, and are quite effective in collecting pollen and nectar. Depending on the floral abundance, season and density of colonies in the area, a single hive may consume 10 to 60 kg of pollen and 55 to 400 kg of nectar per year.

A honey bee displaying its skills in pollen gathering. ©Phonon.b, Wikipedia Creative Commons

Honey bees are efficient pollinators that have been introduced to many parts of the world to improve the yield and quality of crops. But their presence can be bad news for other pollinating species.

Bees can be infected by several viruses and other pathogens such as microsporidia (fungus-like single cell parasites). Every time a bee visits a flower, it risks being contaminated by a pathogen left by a prior visitor. The transmission can go from honey bees to other bees – and even flies – or the other way around, but honey bees are the most likely source of diseases: they are known hosts of many viruses and other pathogens. Besides, large numbers and communal, crowded living arrangements are not the best conditions for keeping diseases at bay, as we humans have recently and painfully learned. Indeed, studies have confirmed pathogen transmission from honey bees to bumble bees and solitary bees. Infections in the opposite direction have been less documented.

A honey bee on a dandelion: risk of diseases for the next visitor. ©Juan Carlos Fonseca Mata, Wikipedia Creative Commons

Honey bees are good at what they do, and the figures prove it: the amount of nectar and pollen collected by a large apiary is sufficient to support 102 bumble bee colonies; during high season (June–August), a 40-hive apiary collects as much pollen as four million wild bees: that means that one hive gathers enough pollen for an average solitary bee species to produce 100,000 offspring. It is difficult to measure whether this level of industriousness has any effect on honey bees’ wild counterparts: bees are highly mobile and cover a huge area while foraging, so it is not easy to set out experiments. Despite this, we have a great deal of circumstantial evidence to suggest there is not enough food to go around when honey bees are in the neighbourhood. 

Every spring, Tenerife beekeepers temporarily move up to 2,700 beehives to Teide National Park to take advantage of the seasonal bloom. A research team saw this cyclical invasion as a great opportunity to evaluate the impact of honey bees. So for three years, they monitored the area before and after beehives were brought in. They observed a clear reduction in the number of pollinator species and diversity of flower visitors when honey bees were present. In other studies in different countries, wild bees switched to less abundant and less rewarding plant species when honey bees were present. Or they became scarcer, gained less weight, and produced fewer and smaller offspring. In other instances, wild bee numbers increased once honey bee hives were removed. In Spain and another 13 countries in the Mediterranean basin, honey bees have become more abundant over the years and are gradually replacing wild bees as visitors of wild and cultivated plants. We don’t know what the consequences are for the 3,300 or so bee species in the region, but it does not bode well. 

Teide National Park, a natural habitat altered by honey bees. ©Mike Peel, Wikipedia Creative Commons

Competition between species happens when food is a limited resource, as is the case for small or isolated areas. That helps explain why native bees have become endangered after honey bees were introduced in New Caledonia (south Pacific), New Zealand, Japan and Tasmania. But competition is not a problem for islands only; it is likely to happen whenever flowers are scarce, such as at the beginning or end of bees’ foraging period, or during unusually cold or dry years.

All of this suggests it is wise to keep honey bees apart from native bees. Introducing or enhancing beekeeping in sensitive areas – that is, those already occupied by scarce or threatened bee species, of semi-natural habitats, or where flowers can be in short supply any time during the season – can put our bee fauna at risk.  

The importance of beekeeping and honey bee pollination is unquestionable, but our wild bee species are important as well, as pollinators and components of our biodiversity. Despite the recent panicked reports in the media about the imminent demise of the honey bee and supposedly mankind, beekeeping around the world has increased by ∼45% during the last 50 years (numbers from America and North Europe are exceptions). Meanwhile, many wild bees have declined for many reasons, including the presence of honey bees.

There are plenty of opportunities for all bees to coexist in our planet: it’s a matter of recognising their potential, limitations, risks and proper place.