Author Archives: Jeff Ollerton

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About Jeff Ollerton

Independent consulting scientist and author, working on understanding and conserving biodiversity

A new study shows how garden flowers keep city pollinators flying all year round

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When we think of cities, gardens might not be the first thing that comes to mind. But these green patches — whether in private yards, parks, or balconies — play a surprisingly important role in supporting urban wildlife. Among their most crucial guests? Pollinators like bees, butterflies, and even birds and bats.

In a new study just published, I teamed up with some Brazilian colleagues to explore how the different features of garden flowers help sustain pollinators throughout the year in a subtropical urban garden. While we’ve long known that garden flowers provide food for pollinators, what’s less clear is how specific floral traits — like shape, flowering time, and type of nectar or pollen — influence who visits which plants and when.

To get a clearer picture, we conducted weekly surveys of pollinators visiting garden flowers over the course of a year. We paid close attention to traits such as the depth of flower, the kind of resources offered (nectar vs. pollen), how closely related different plants were, and when they flowered.

What we found was striking: the network of interactions between flowers and pollinators was highly organized. Plants grouped into clusters, or “modules,” that tended to share similar physical traits and evolutionary histories — but interestingly, not the same flowering times. This meant that within each module, different plants flowered at different times of year, effectively staggering their blooms so that there was always something on offer for pollinators.

Even more intriguing was the discovery that most plants had just a few connections in the network, usually restricted to a single module. These “peripheral” plants accounted for over 85% of all pollinator visits. Meanwhile, a few special species acted as bridges between modules — their role in linking different parts of the network made them key to its stability. These connector species didn’t flower at the same time, which helped to maintain a steady supply of food for pollinators across seasons.

Not all interactions between plants and pollinators are “legitimate” in the sense of leading to pollination. Some animals visit flowers just for the food, without helping with reproduction. But our study found that these interactions still played a valuable role in supporting a diverse pollinator community.

So what does all this mean for urban gardeners and city planners?

First, it highlights how important it is to plant a variety of flowers that bloom at different times of year. Second, it shows that even seemingly minor plants or interactions can contribute to the ecological resilience of urban green spaces. And finally, it underscores that thoughtful planting — considering things like flower shape, blooming schedules, and diversity — can help keep pollinators thriving, even in the heart of the city.

Urban gardens aren’t just pretty — they’re powerful allies in the fight to support biodiversity.

The study was led by Brazilian research student Luis de Sousa Perugini. Here’s the reference with a link to the paper:

de Sousa Perugini, L.G., Jorge, L.R., Ollerton, J., Milaneze‑Gutierre, M.A. & Rech, A.R. (2025) High modularity of plant-pollinator interactions in an urban garden is driven by phenological continuity and flower morphology. Urban Ecosystems 28, 126

Here’s the abstract:

Garden flowers play a vital role in urban environments, supporting pollinator communities. Yet, the extent to which floral traits shape urban pollination networks remains poorly understood. This study investigated how garden plants shape year-round pollination networks, sampled in weekly surveys in an urban subtropical garden. We focused on the role of floral morphology (corolla depth), type of resource, relatedness, and phenology in the organization of interactions. We determined whether modularity and species roles were influenced by these floral traits, comparing if legitimate pollination, illegitimate (i.e. non-pollinating) interactions and all interactions had similar drivers. All networks were modular, and in the overall network plants within the same module were morphologically and phylogenetically similar while their phenology was significantly overdispersed throughout the year. Peripheral species, those with few interactions and restricted to a single module, dominated all networks, representing over 85% of interactions. We found that phenology was related to the species role of overall network connectors (species that connect modules) and legitimate module hubs (species that connect their own modules). Both showed no overlap in their flowering periods, providing floral resources at different times of the year. Each module functioned as a distinct unit, showing year-round availability of resources to support its pollinators. This suggests that resource continuity and trait-based filtering may shape pollinator assemblages influencing ecological resilience in urban habitats. Even interactions that do not contribute to plant reproduction can sustain a diverse fauna, highlighting the importance of these interactions in urban green space planning and management.

The Black Cats go green, and go up!

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It’s impossible to be a native of Sunderland and not to have at least a passing interest in football. If you’ve seen the Netflix series Sunderland ‘Til I Die, you’ll know that in my home town, football is more of a religion than a leisure activity. It’s a passion that extends back to the foundation of Sunderland Association Football Club (SAFC) in 1879, whose nickname is the Black Cats.

Growing up, football was always a topic of discussion in our house. My dad played Sunday League football for many years and my Uncle Gordon Howe was a professional footballer. But to the general disappointment of my family, I’ve never had a deep interest in the sport, though I do keep a watch on how well the team of my birthplace is doing. And as of yesterday they are doing extremely well! The team beat Sheffield United (ironically, one of the teams that Uncle Gordon played for) in a thrilling, close-run match to earn promotion back into the Premier League. I watched it live with friends in a local pub, and there was a great reception to the win, even among customers who had no vested interest in the club.

It brought back memories of the mid-1970s when I attended matches at SAFC’s old Roker Park stadium, buoyed up by the club’s ‘giant killing’ win over Leeds United in the 1973 FA Cup Final. But even after my childhood interest in football waned, replaced by a growing fascination with natural history, home matches were frequently a backdrop to Saturdays. The famous Roker Roar always signaled that the team had scored. That shout echoed across the town and down through the Magnesian Limestone gorge of the River Wear, part of which you can see in the photograph above. Exploring the exposed geology, and the grassland and brownfield habitats of that river valley, is an important reason why I became an ecologist, as I recounted on the blog a decade ago.

The shot was taken in early 1986 and it shows the view from the back of the house in which I grew up. On the south side of the river, you can see cranes and sheds associated with the shipbuilding industry, for hundreds of years one of the two main engines of the local economy. Directly ahead, situated on a promontory, you can see an example of the second engine: Wearmouth Colliery, a 2,000 ft deep coal mine that extended out under the North Sea. The mine employed quite a number of members of my family, including my grandfather and several uncles*, one of whom was killed in the early 1900s after a pit pony kicked him. My dad was also a miner for a time but he worked further up river at the Hylton Colliery, which produced more than its fair share of professional footballers, as well as coal.

In 1993 Wearmouth Colliery closed and the site was quickly cleared – see this amazing set of photos that was taken at the time. Four years later, SAFC closed Roker Park and moved to a new purpose-built stadium on the colliery site. They called it The Stadium of Light, a name that honours the ‘miners at Wearmouth Colliery [who] carried with them a Davy lamp as part of their working lives’. Here’s a shot of the stadium perched above the river, taken by my good friend Mark:

Not only have Sunderland gone up, they have also gone green, with a commitment to be carbon neutral and generate their own power from solar installations (though that scheme has attracted some controversy). They are also making the team’s kit from recycled plastic bottles and looking at more environmentally friendly ways of dealing with match day waste – see this press release on their ‘Ready Eco’ initiative. There’s also a plan to tap into the geothermal potential of the mine to heat local houses, though that has been delayed, unless anyone has more recent news on the scheme?

Biodiversity, always the Cinderella of environmental mission statements, is missing from that initiative, which is a shame because the stadium lies adjacent to some very interesting habitats. To the left of the stadium, on the steep slopes of the gorge, you can see patches of Magnesian Limestone Grassland, a relatively rare plant community that is virtually confined to the North East of England.

This minor gripe aside, it’s great to see Sunderland being promoted and taking a lead in thinking about how football as the national sport has an environmental impact. It makes me even prouder of my home town.

*When I was researching this post I came across the following article from the local newspaper. It mentions my Uncle Walter Ollerton who earned a safety badge that is still in my possession. At the outbreak of World War 2 he enlisted and fought in the Far East, where he was captured by the Japanese and held in a prisoner of war camp. After his release he returned to his job as a miner in Sunderland, but his health was never the same:

Have we passed “peak honey bee” in Britain? An update of hive numbers for World Bee Day 2025

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Since publishing what I believe are the most comprehensive data on the number of honey bee hives in Britain in my book Pollinators & Pollination: Nature and Society, I’ve posted occasional updates on my blog as more recent data become available. I believe that the last of these was in 2022 – see Have honey bees declined in Britain? An update of the numbers – so it feels like it’s time for another. And what’s more appropriate than to post this on World Bee Day 2025?!

Rather than the complex, multi-coloured graph that I’ve produced in the past, I’ve decided to streamline the presentation and simply fit a smoothed LOESS line with a 95% confidence ribbon to the (sometimes contradictory) data points, in order to show the overall trend (see the graph above). If you compare it with the 2022 update you’ll see that the general message from the data is the same: a peak in numbers of hives in the late 1940s (which may or may not be an artefact*), then a steep decline into the 1970s and 1980s, followed by recovery from the 1990s onwards. Note that I’ve removed the two very early data points because I don’t think that they are at all accurate.

The most recent data (2015 to 2024) come from the National Bee Unit which relies on beekeepers to submit their own records, but are probably no less accurate than some of the other data that’s available! If we take a close look at that time period we see something interesting – honey bee hive numbers are decreasing:

What are we to make of this? In an analogy with peak oil, why do we seem to have passed ‘peak honey bee’? If this is a real pattern (and only time will tell) I suspect that it’s because of at least two factors. The first is that interest in beekeeping reached a peak in the early 2020s, after which some initial enthusiasts discovered that beekeeping is actually quite a technical and demanding hobby, and gave it up. The second factor is that word has spread that, globally, managed Western honey bees are not declining, and too many bee hives in an area can have negative impacts on other, wild pollinators. This may have convinced those people who were persuaded by “Save the Bee” campaigns to take up the hobby, to give up beekeeping.

There could well be other reasons that I’ve not considered and, as always, I’d be interested in your thoughts – please leave a comment below. I’ll finish by saying that I make no judgement on this. There’s no doubt that there are too many hives in some parts of Britain, especially in London, and if the trend I describe reduces the pressures on wild pollinators, that’s a good thing. At the same time, honey bees are important agricultural pollinators in some circumstances, especially where there’s mass-flowering crops that require huge numbers of pollinating bees to be available over a short time period. And I like honey as much as the next person.

Happy World Bee Day to my readers!

*There’s a long-standing suggestion that beekeepers in the post-war years inflated the number of hives that they kept in order to obtain a larger sugar ration.

‘Why Do We Need Worms?’ long-listed for the School Library Association Book Awards!

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Since early 2021 I’ve acted as a science advisor for some of the children’s books published by Usborne, beginning with Can We Really Help the Bees? The most recent is Why Do We Need Worms?, written once again by Katie Daynes and with amazing illustrations by Moesha Kellaway. I’m especially proud of my involvement with this book as in its early stages I suggested mentioning Charles Darwin’s fascination with worms. The book is aimed at ages 4 and upwards, though a reviewer has said that it’s ‘Perfect for my 3 year old grandson who loves looking at worms!’ So this book has to have one of the youngest Darwin readerships!

Why Do We Need Worms? was published last year and I’m delighted to say that this year it’s been long-listed for the School Library Association Book Awards in the 0 to 7 years Information Book category! It’s a great achievement for everyone involved and if the book gets short-listed, I will be sure to let you know.

Mindful Mow May!

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As April comes to a close, many people with gardens will be considering having a No Mow May in which, to quote Plantlife (who have trademarked the phrase!), you ‘pack away the lawnmower, let wildflowers grow freely and help nature’. On the face of it this is a positive thing and (hopefully) it gets people thinking a bit more about the impact of gardening practices on wildlife. However, I do worry that its message is too simplistic, as I’ll explain in the rest of this post. Let me say at the outset that I’m using the word ‘mindful’ in its sense of ‘paying attention to’, rather than in relation to mental health mindfulness. Though there are certainly connections between lawns and both meanings of this word, for example mindfully watching pollinators in your garden.

I’ve previously written about the garden that Karin and I developed in Northampton, including a ‘defence’ of its lawn. During the lockdown spring and summer of 2020, when I coordinated a loose consortium of scientists to collect standardised data on the flowers and pollinators in their own garden, our lawn was one of the areas that I surveyed. In that year, as every year, we had no intention of not mowing the lawn, but of mowing it in a mindful way that left some flowering patches of the main nectar sources: Dandelion (Taraxacum officinale), White Clover (Trifolium repens), and Daisy (Bellis perennis). It also allowed a patch of Common Ragwort (Jacobaea vulgaris), and the Cinnabar Moths (Tyria jacobaeae) that depend on it, to come back year after year.

In the graph below you can see the nectar production of dandelions, clovers and daisies over the course of the late spring to late summer. For each species, I have multiplied the number of flower heads I counted by the average amount of nectar sugar per flower head from the data collected by the Agriland project. Clover produces 48.97 micrograms of sugar per day, by far the highest amount of the three. Daisy produces the least, just 0.84 micrograms, and dandelion is in the middle with 22.57 micrograms.

Because these species vary in their peak flowering, there’s a continuous supply of nectar in the lawn over this time period and mowing does impact the immediate availability of nectar. Using green shading, I’ve marked the two days when I know for certain the lawn was mown and you can see that there’s an immediate drop in the nectar. Here you can also seen that both dandelions and daisies re-flower quite soon afterwards – it’s not a permanent effect by any means. The same is probably true of clover later in the season, but unfortunately I didn’t record the exact mowing dates.

The important thing to appreciate here is that without mowing, these three species would probably disappear from the lawn because all require that grasses are suppressed in order for them to flourish. Not only that, but most ground-nesting bee species need either very short turf or bare soil in which to nest. And most bees, at least in the UK, are ground-nesting.

The image at the top of this post is from my book Pollinators & Pollination: Nature and Society, and it shows two views of the same grassy, south-facing bank in Kettering, Northamptonshire. I included it because it’s a nice example of the mindful approach to lawn mowing that I am describing: bees are able to nest in the low-cut turf and collect the nectar and pollen from the flowers in the unmown areas. Later in the season that unmown area will be cut. This is referred to as ‘matrix mowing’, which is to say that by cutting some areas and leaving others, you create a matrix of different lawn lengths that has a greater overall benefit than is obtained by either cutting everything at the same time or cutting nothing for a whole month. It’s even better if you have the space to leave some patches unmown for a year or two. That way you create longer grassy areas in which insects can over winter and some bumblebees can nest.

It’s worth mentioning at this point that I know of only one published study that’s assessed the impact on No Mow May on pollinators, and that study was retracted shortly after it appeared. If I’ve missed other studies please do let me know in the comments.

I’ll finish with the Royal Horticultural Society, which was in the news recently with an announcement that it’s collaborated with gardener Monty Don to come up with ‘hard-wearing flower lawn that is good for pollinators, dogs and people’. This is hardly rocket surgery, it’s the sort of diverse, low-input, low maintenance lawn that many of us have been advocating for years, but if it brings these ideas to popular attention, so much the better.

So, consider engaging in Mindful Mow May* (and April, and June, and all the other months!) As always, feel free to comment below or get in touch with me via my Contact page.

*In the past I’ve also used the term “Matrix Mow May” which amounts to the same thing – being mindful of exactly where is mown and where is not.

Project ‘Butterfly’ takes flight in Paris!

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At the end of last week I joined researchers from across Europe and beyond who gathered at Norway House on the campus of the Cité Internationale Universitaire de Paris, for the official launch of the EU-funded project ‘Butterfly’. This bold, four-year interdisciplinary initiative is focused on the future of pollinators and the ecosystems that depend on them, and is one of a series of projects that have spun out from the EU’s Pollinators Initiative.

Over two days of lively discussion, the project’s key themes came into focus: the urgent need to restore pollinator populations, the value of integrating ecological and economic data, and the importance of including people—farmers, citizens, policymakers—in shaping practical, long-term solutions to pollinator decline.

Connecting Science and Policy

I arrived in Paris early Wednesday evening to be fresh for the meeting’s opening session the following morning. This set the stage by grounding the project in real-world policy contexts, including the EU Pollinators Initiative and the Nature Restoration Law. These frameworks are increasingly recognising the vital role pollinators play not just in nature, but in the economy and public well-being.

Nine Work Packages, One Mission

Participants got a crash course in the project’s structure through short presentations from each of the nine work packages. These range from ecological modelling and ecosystem valuation to resilience thinking, communication tools, and understanding human relationships with pollinators. A strong emphasis was placed on collaboration—how each work package connects with the others and contributes to the project’s broader vision. For example, one of my roles will be to work closely with Maria Clara Castellanos and her team at the University of Sussex on the integration of the UK-focused Database of Pollinator Interactions (DoPI) and the Global Biotic Interactions (GloBI) platform, to create an online European Atlas of Plant-Pollinator Associations (EuroAPPA). This in turn will feed plant-pollinator data into the modelling and economic valuation tasks in some of the other work packages.

Living Labs and Global Perspectives

One of the most exciting aspects of the Butterfly project is the network of “Living Labs” being established across Europe and the test sites in overseas territories. From Murcia to Martinique, each site represents a unique ecological and cultural landscape with its own pollination challenges. These test sites, some of which are shared with a parallel project called RestPoll, will serve as experimental spaces to co-develop and test strategies for enhancing pollinator resilience in real-world contexts. Another of my roles in the project is to help with the field work on the Caribbean island of Curaçao, where we will be assessing birds and bats as pollinators, as well as insects.

Thematic Sessions and Cross-Pollination

The meeting featured targeted discussion sessions on everything from economic modelling chains and ecosystem indicators to human dimensions like eco-literacy, historical agency, and “slow hope.” Again, one of my contributions will be to the work package dedicated to understanding and reacting to the human dimensions of pollinator decline, where I hope to provide a case study that builds on the work I published almost a decade ago on how the auction prices of holly and mistletoe are a reflection of the work of wild pollinators. In the evening we had a “cross-pollination” networking buffet dinner, themed around pollinator-dependent food crops, that provided an opportunity for participants to mix across disciplines, brainstorm, and spark new collaborations in an informal setting.

Laying the Groundwork for Action

Day two shifted toward practicalities—data sharing, financial management, ethics, and stakeholder engagement—as well as discussions about how Butterfly will connect with other major EU-funded projects, including VALOR, which is Butterfly’s partner and with which we will closely collaborate. Thematic sessions continued to dive deep into topics like mainstreaming pollinator stewardship and developing indicators to track the societal impacts of pollinator loss.

Looking Ahead

The meeting wrapped up with a plenary session with the project’s Advisory Board, reinforcing the importance of external perspectives in guiding the project’s evolution. Dinner that evening was an informal affair (not funded by the project!) at a really wonderful, traditionally French restaurant – Le Temps des Cerises – where service was slow, the food and wine were delicious, and the conversations continued to flow.

For those of us who stayed an extra day, a field visit on Saturday offered a first-hand look at urban pollinator research at the Jardin Écologique within the Jardin des Plantes—a fitting reminder of why this work matters! Here’s some photographs from that trip:

My sincere thanks to all of the colleagues who made the Butterfly kick-off meeting such a success: I look forward to working with you all over the next four years! Particular thanks to Paolo Biella who allowed me to use the photo at the top of the post, of a female mason bee outside our venue. We kept an eye on her during the meeting and I’m pleased to report that she successfully sealed up her nest. May her offspring thrive!

If you’d like to delve deeper into Butterfly’s objectives, here’s the project summary from our funding application:

Butterfly aims to significantly enhance society’s capacity to appraise, foresee, and respond to the threats posed by cascading impacts of pollinator decline. To reach that goal it will establish a test system of geographically well spread multi-actor communities across sectors for co-creating proactive pollinator restoration solutions and: (1) collect, integrate, manage and share ecological and spatial information on a wide range of known and lesser known pollinators and pollination services provided for wild and cultivated plants, across Europe and selected overseas territories; (2) advance the monetary and non-monetary valuation of marketed and not marketed direct and indirect ecosystem functions and services provided by pollinators, and advance ecosystem accounting; (3) comprehensively model and quantify the macro-economic implications of pollinator decline and country-specific economic butterfly effects of dependencies on pollinators, and assess policy options and scenarios; (4) assess how five key biomass supply chains (food/micronutrients, pharmaceuticals, cosmetics, biomaterials, biomass energy) depend on pollination and co-create pollinator restoration options that increase resilience of these supply chains; (5) devise, co-create, test and implement transferable tools, interactive atlases and guidelines that enable systematic mainstreaming of proactive pollinator stewardship in vulnerable sectors; (6) conceive indicators for human dimensions and assess and exploit the socio-cultural capacity of the concepts: ‘pollinator stewardship’, ‘ecoliteracy’, ‘historical agency’ and ‘slow hope’ in reversing pollinator decline. It will inform EU policy processes and build strategic alliances for high-level impact. The Butterfly network of Living Labs will accelerate knowledge transfer and uptake of new business models and serve as breeding place for multi-actor co-creation of knowledge and sustainable solutions, paving the way to pollinator stewardship in all sectors.

Is Biodiversity Net Gain a missed opportunity for invertebrate conservation? A new open access study suggest ways to improve it

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The UK has set ambitious targets under the Global Biodiversity Framework 2030, aiming to halt and reverse biodiversity loss. One of the key policies designed to help achieve this is Biodiversity Net Gain (BNG), a requirement in England that ensures new developments (such as housing projects) result in a 10% increase in biodiversity. On the surface, this sounds like a positive step—but is it really working for all species?

In a newly published paper that I co-authored, led by University of Oxford PhD student Natalie Duffus, we suggest that BNG may be falling short for some of the most vital, yet overlooked, members of our ecosystems: invertebrates. This group includes insects, spiders, and other arthropods—organisms that play critical roles in pollination, pest control, and nutrient cycling but are also experiencing dramatic population declines worldwide.

The Problem with a Habitat-Focused Approach

The way BNG is currently applied focuses heavily on habitats rather than species, meaning that while new green spaces may be created, they may not necessarily provide the right conditions for invertebrates to thrive. In some cases, BNG could even make things worse by fragmenting existing habitats or failing to account for the complex ecological needs of different species.

For instance, many invertebrates rely on very specific plants, soil conditions, and microhabitats that a broad-brush approach to habitat restoration may not support. Simply increasing the area of green space does not guarantee it will be suitable for pollinators, decomposers, or predatory insects that help keep ecosystems functioning. It’s an issue that I highlighted in October 2023 when I wrote a report about BNG and pollinators.

How Can BNG Be Improved?

Rather than being a one-size-fits-all approach, BNG could be better aligned with evidence-based conservation strategies, such as the National Pollinator Strategy. By integrating more targeted actions—including planting native wildflowers, preserving deadwood for beetles, or ensuring hedgerows and wetlands remain intact—BNG could deliver real benefits for invertebrates.

Additionally, better monitoring and evaluation are needed to track whether biodiversity is genuinely improving under BNG policies. This would help policymakers refine their approach and ensure conservation efforts support the widest possible range of species, not just the most obvious or easily monitored ones.

Lessons for Global Conservation

With many countries looking to adopt biodiversity offsetting schemes like BNG, England’s experience offers valuable lessons. If BNG is to be truly effective, it must take a more holistic, species-specific approach—one that recognizes the essential role of invertebrates and actively works to protect and enhance their populations.

If done right, BNG could be a game-changer for conservation. But if we fail to consider the full picture, it risks becoming a well-intentioned policy that does little to halt biodiversity loss where it matters most.

Here’s the full reference with a link to the paper – it’s open access and can be downloaded for free:

Duffus, N.E., Lewis, O.T., Grenyer, R., Comont, R.F., Goddard., D., Goulson, D., Ollerton, J., Townsend, M.C., Webb, J.A., Wilson, R.I. & zu Ermgassen, S.O.S.E. (2025) Leveraging Biodiversity Net Gain to address invertebrate declines in England. Insect Conservation and Diversity (in press)

Is Common Elder an under-appreciated habitat for bats? [updated]

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Regular readers of my blog may recall that I have an obsession with something of an interest in Common Elder (Sambucus nigra) that goes back to my childhood, as I recounted in an article for British Wildlife back in 2022. In that article I mentioned that the larger hollow trunks and branches of elder “can offer nesting opportunities for birds and small mammals”, but didn’t go into detail. The mammals I was thinking of at the time were small rodents, but following a long country walk with Karin recently I wondered whether bats might also make use of these hollows as roosts for breeding and/or hibernation.

I posed this as a question for the bat specialists in the British Ecologists Facebook Group and received several replies, with respondents mentioning that they had encountered Natterer’s Bat (Myotis nattereri), Common Pipistrelles (Pipistrellus pipistrellus), and Brown Long-eared Bat (Plecotus auritus), in hollow elder trees, during summer and autumn surveys.

A couple of people suggested that I check out Arbology’s Look-up Tool for the Bat Tree Habitat Key (BTHK) database which records trees that are used by bats, but to my surprise it returned the following message:

“There are no positive results which match your query.
This does not mean that bats won’t use the feature type in the species and habitat you have selected, but current data suggests that survey effort may be better focused on features which have a proven occupation”. 

The BTHK relies on bat surveyors adding their observations, but clearly no one has submitted records of bats in elder, despite the fact that we know they occur. This concerns me for two reasons.

Firstly, of all of our smaller native woodland edge and hedgerow trees, elder is (in my experience) the one most likely to have significant cavities in their trunks and branches. The specialists in the Facebook Group introduced me to the phrase “if they fit, they sit”, meaning that almost any cavity might contain bats, even quite low to the ground: one respondent mentioned that a friend had found two Common Pipistrelles during an autumn survey, in a dead elder stem less than ten centimeters in diameter at about one metre above ground level.

Secondly, it’s not unusual for old elder trees to be cut right to the ground or even removed completely during work on hedgerows. It’s a neglected, even despised native British tree that, as I noted in that British Wildlife article, is:

“generally considered by naturalists, when it is considered at all, as rather boring, so commonplace that we hardly give it a second glance…[and by some as]…’barely a tree at all, more of a weed'”

Another respondent mentioned that ​tubular structures, such as elder branches, are less likely to be identified as active bat roosts in the absence of bats, as they provide limited shelter and often lack droppings, which tend to fall out, leaving minimal evidence. I’m sure that’s not the whole story, however, I think it’s more likely that small trees generally are overlooked when it comes to habitat for bats: the BTHK has a single entry for Common Hawthorn (Crataegus monogyna) and nothing for Blackthorn (Prunus spinosa), for instance.

In addition to bats, another respondent noted that Willow Tits (Poecile montanus), a species experiencing significant decline and now red-listed in the UK, often nest in elder trunks, where they excavate cavities in decaying wood. That’s yet another reason why we should pay more attention to this most interesting of trees!

My thanks to all of the British Ecologists who replied to my query. As always, feel free to comment or get in touch via my Contact page.

UPDATE: After I posted this on Bluesky, Richard Broughton, author of The Marsh Tit and the Willow Tit, pointed out that elder is also a significant nesting site for Marsh Tits (Poecile palustris), another red-listed species. To quote Richard’s comment:

“Elder is prob[ably] the very best cavity-bearing shrub, far better than hawthorn, hazel, blackthorn (very poor). Important nesting shrub for Marsh Tits & Willow Tits, but only if left to develop old trunks and cavities, not cut. Like Hazel, they self-coppice without management, with new growth from base….in Wytham Marsh Tit studies Elder was the main nest tree/shrub. Though it’s not common/available in woods everywhere. It develops *really* good hollow nest cavities for the small hole-nesting guild, and also very amenable for Willow Tits to excavate. Prob[ably] important in hedges, where holes rare.”

Richard kindly shared a scan from his book showing that for Willow Tits, elder ranks second (after willow and birch) and for Marsh Tits it ranks second after Ash.

Evolutionary implications of a deep-time perspective on insect pollination – a new review just published

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When we think of pollination, we often picture bees buzzing around flowers or butterflies flitting from bloom to bloom. This relationship between plants and pollinators is one of the most well-known interactions in nature. But insect pollination didn’t begin with the colorful flowers we see today. In fact, pollinators were at work millions of years before flowering plants (angiosperms) even existed. In a new review led by Spanish researchers David Peris and Ricardo Pérez-de la Fuente, to which I added a modern ecological perspective, we explored this topic and why it’s relevant to our current understanding of plant-pollinator relationships.

Despite centuries of research on pollination, the fossil record of pollinating insects has only gained serious attention in the past few decades. What palaeontologists have uncovered is reshaping our understanding of pollination’s origins. It turns out that insects were pollinating plants long before flowers evolved—playing a crucial role in the reproduction of ancient gymnosperms, the group of seed-producing plants that includes conifers, cycads, and ginkgos.

Most people assume that insect pollination began with flowering plants, but the evidence tells a different story. Fossilised insects with specialised body structures for carrying pollen—such as hairy bodies or mouthparts adapted for nectar-feeding—have been found in deposits dating back hundreds of millions of years. These early pollinators likely visited gymnosperms, helping them reproduce in a world that looked vastly different from today’s landscapes.

Ancient pollination was driven by a diverse range of insects, many of which are now extinct. The fossil record reveals that various insect groups—including beetles, flies, wasps, and even some long-lost relatives of modern lacewings—were already acting as pollinators long before the first flower bloomed. This means that pollination as an ecological process has far deeper evolutionary roots than many realise.

As plants evolved, so did their pollinators. The rise of flowering plants during the Cretaceous period (around 100 million years ago) transformed pollination systems, leading to the incredible diversity of plant-pollinator relationships we see today. Many of the insect groups that once dominated pollination in prehistoric times have since declined or disappeared, replaced by the bees, butterflies, and other familiar pollinators that thrive in modern ecosystems.

Understanding this long history is essential—not just for scientists, but for anyone interested in biodiversity and conservation. When we focus only on present-day pollinators and plants, we miss a crucial part of the story. The fossil record helps us see how pollination has changed over time, which in turn can offer insights into how today’s ecosystems might respond to environmental pressures such as climate change and habitat loss.

Recognising the ancient history of insect pollination isn’t just an academic exercise—it has real-world implications. If we understand how pollination evolved and adapted to past environmental changes, we can better predict how it might shift in the future. Conservation efforts that aim to protect pollinators today can benefit from a long-term perspective, ensuring that we’re not just responding to recent trends but also considering deep-time ecological processes.

So the next time you see a bee visiting a flower, remember—you’re witnessing the latest chapter in a story that began hundreds of millions of years ago. The relationship between plants and pollinators is far older, more complex, and more fascinating than we ever imagined.

Here’s the reference with a link to the paper. It should be open access, but if you have problems obtaining it, send me a message via my Contact page:

Peris, D., Ollerton, J., Sauquet, H., Hidalgo, O., Peñalver, E., Magrach, A., Álvarez-Parra, S., Peña-Kairath, C., Condamine, F.L., Delclòs, X. & Pérez-de la Fuente, R. (2025) Evolutionary implications of a deep-time perspective on insect pollination. Biological Reviews (in press)