Tag Archives: Gardening

Big Garden Birdwatch – our first six years of data

Big garden bird watch

This morning I spent an hour gazing out of our bedroom window with a coffee, a notebook, and a pair of binoculars. Not sure what the neighbours opposite us thought I was doing but I was happy – this weekend is the RSPB’s Big Garden Birdwatch! I’ve taken part in it every year since Karin and I moved into our present house in February 2012, and I thought it was time to show the results to date.

As you can see in the graph above, for the first couple of years there were relatively few birds (only 6 species in 2013, 8 in 2014). Then in 2015 it jumped to 15 species, including some that I’ve not recorded in the garden since such as Lesser redpoll. Two reasons for this sudden increase I think. First of all, January 2015 was particualrly cold which meant that more birds were moving into urban areas looking for food and a little more warmth. But secondly, and the reason why higher bird diversity has been maintained since then, is that we’ve been developing the garden and planting more shrubs, small trees, etc.

So since 2012 we’ve gone from this:

2012-02-22 10.19.23

To this:

The garden 20180127_114638.png

This planting and development of the garden has been good for other wildlife including bees, butterflies and other pollinators, as I’ve recounted a number of times. So here’s a close up from last summer just to remind us that, on this grey, drizzly January day, spring is not so far away:

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Of course you don’t need to have a garden to take part in the Big Garden Birdwatch – the RSPB also accepts data from surveys of public parks and green space. In fact tomorrow morning I’m leading a group of residents around our local park, The Racecourse, to do just such a survey.

Right, must go and upload this years data to the RSPB’s site.

Some upcoming public lectures

Garden pollinators for PAW no. 6 – Buff-tailed bumblebee (Bombus terrestris)

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It would be impossible to write a series of blog posts about garden pollinators for Pollinator Awareness Week without considering the bumblebees (genus Bombus) and I intend to devote the last two posts to that group of bees. The bumblebees are arguably the UK’s most important pollinators of both wild and crop plants, certainly later in the season when colony numbers have increased. Earlier in the season it’s the solitary bees such as the Orange-tailed mining bee that are predominant.

Although common and widespread in gardens, the Buff-tailed bumblebee (Bombus terrestris) belongs to a group of bees in which the workers are rather variable in appearance and can be very difficult to distinguish from those in the Bombus lucorum group, which includes two other species (B. cryptarum and B. magnus).

This is a truly social species with an annual nest comprising workers and a queen. Nests are founded by queens that have mated the previous year and hibernated. They usually choose old rodent nests in which to begin their colonies, which is why they are sometimes found in garden compost bins. An interesting question that I’ve not seen answered is whether the queens actively displace mice or voles from such nests: does anyone know? This association between bumblebees and mice led Charles Darwin and Thomas Huxley into some speculation as to the role of spinsters in the British Empire.

In my garden the Buff-tailed bumblebee pollinates a range of crops including strawberries, squashes, courgettes, blackberries, runner beans, french beans, tomatoes, and raspberries. As the photo above shows they also visit the flowers of passion fruit, where they seem to be more effective than the smaller honey bees and solitary bees.

Garden pollinators for PAW no. 4 – Gatekeeper butterfly (Pyronia tithonus)

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For my fourth contribution to Pollinator Awareness Week I’m going to highlight the Gatekeeper (Pyronia tithonus), a butterfly that I featured on this blog last year. As I noted in that post, it’s fairly rare to have Gatekeepers in an urban garden which indicates that the shrubs and hedges grown by myself and my neighbours are providing the right microclimate for the adults. In addition the overgrown lawns of some adjacent gardens give opportunities for egg laying as the caterpillars are grass feeders.

Adult butterflies are very well camouflaged when resting with their wings folded. They take nectar from a range of plants in my garden but particularly love the dark, heavily scented infloresences of the buddleia variety pictured here. They also visit the wild blackberries scrambling through the hedge that separates us from next door’s garden and probably pollinate those flowers. Although it’s often said that butterflies are poor pollinators compared to bees, due to their general un-hairiness and habit of holding themselves above the stamens and stigmas in a flower, it very much depends on the type of flower. We have an unpublished manuscript that I hope to submit to a journal later this year showing that butterflies are actually better pollinators of one grassland plant than bumblebees.

Garden pollinators for PAW no. 1 – Patchwork leaf-cutter bee (Megachile centuncularis)

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As promised, here’s the first of my posts for Pollinator Awareness Week and I’m going to start with one of my favourite groups of bees – the leaf-cutters of the genus Megachile. The UK has only nine Megachile species recorded, several of which are quite frequently found in gardens.

In my urban garden in Northampton I’ve often encountered the Patchwork leaf-cutter (Megachile centuncularis) this summer. As you can see from the link to Steve Falk’s excellent photographs and description of the species, it’s quite distinctive with a brush of orange hairs that extends right to the tip of the abdomen (see the first picture, though the colour of this can fade with age so it’s not always so apparent). The brush is used for collecting pollen from flowers to take back to provision its nest, which is constructed from leaf segments lining a tubular cavity in old walls, wood or occasionally soil (hence “leaf-cutter” bees). The leaf-cutters (as with 90% of bee species) are “solitary” in the sense that they don’t have a social structure with a communal nest, a queen, etc. It’s the female bees that are solely responsible for nest building; the purpose of the males is simply to mate.

I’ve seen this species visiting my runner beans in the garden and, given their size, they probably pollinate that crop, though not as effectively as bumblebees which are much more abundant.

In the image above you can clearly see the pollen that’s been collected by this bee under its abdomen.

In my garden the Patchwork leaf-cutter is very fond of Lamb’s ear (Stachys byzantina), but I’ve seen it collecting nectar and pollen on a wide range of other plants too.

Garden chickens and biodiversity – some thoughts

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Keeping chickens as a hobby is very popular at the moment and many gardeners are finding space for a few chooks in their own patch. It’s been particularly trendy amongst urban gardeners, ourselves included: we have a run with 6 hens that make us self sufficient in eggs and chicken shit (the latter a vital addition to our soil’s fertility). They are also fascinating, relaxing animals to watch as they go about their chickeny business of scratching, pecking, clucking, and dust bathing. They are intelligent, social, inquisitive birds, that I’d recommend to anyone who has the space to accommodate a decent sized run and (importantly) the time to look after them.

There are plenty of magazines, books and websites offering advice on keeping hens on a small scale. One of the most active and interesting blogs is The Garden Smallholder which generally has some good advice and ideas. Back in November, however, a post about preparing a new kitchen garden caught my attention, specifically the fact that the writer’s chickens were let out onto the plot and that:

“Chickens are great at scratching and turning over soil with their enthusiastic feet, and excellent pest control too”

Let’s think about that last point, that chickens provide “excellent pest control”. It’s a statement that I’ve seen repeated many times in books and articles, and it usually doesn’t solicit any comments. But the logic behind it is that hens can differentiate between “pests” and “non-pests” in a garden, that they will gobble up the slugs and cutworms, leaving behind the worms, beetles, spiders, and other beneficial (or neutral) invertebrates. This is nonsense, of course: chickens will eat anything they find and do not differentiate between the different elements of soil biodiversity*.

For this reason we don’t allow our hens to free range on our vegetable patch: we want to keep the soil’s fauna intact, allowing the earthworms to aerate and turn over the soil, let the beetles eat the slugs, give ground-nesting bees some space in which to live, and so forth. A few weeks of digging with chickens present would destroy all of that.

The vast majority of invertebrates that live in the soil are not pests and a significant proportion are certainly good for our gardens (particularly the earthworms and carnivorous beetles). Allowing your chickens to feed freely on these animals will significantly reduce your soil biodiversity, which is a bad thing in its own right (if we accept that these animals are a measure of your soil’s “health” and productivity), and could reduce the numbers of invertebrate-eating wildlife, such as thrushes, hedgehogs and toads, visiting your garden.

If you want your chickens to eat garden pests my advice would be to take the pests to them: scoop up several slugs with a trowel, throw them into their run, and watch the birds excitedly scramble for their treat. But remember that slugs play a positive role in the garden too, demolishing huge amounts of garden waste in compost bins and (in our garden) eating up cat shit. That’s a topic for a future post though.

*I made a comment to this effect on the Garden Smallholder post but the blog owner saw fit not to allow it to appear. Draw your own conclusions from that.

Gatekeeper in the garden

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Since moving into our house in January 2012 I’ve been keeping a list of butterflies and day-flying moths seen in the garden (as well as birds and bees, of course). That list currently contains 14 species*, one of the most interesting of which is the Gatekeeper (Pyronia tithonus).

According to the account of this species on the UK Butterflies web site, the Gatekeeper:

“can be found wherever shrubs grow close to rough grassland. ……some of the largest colonies can be found at field edges and along hedgerows and we can expect to find this butterfly in scrubby grassland, woodland rides, country lanes, hedgerows and the like anywhere within its range”.

So what is it doing in an urban garden? The BTO’s summary of the species mentions that:

“It is rare for Gatekeepers to appear in city-centre gardens. However, in recent years this species has been recorded at some urban sites across north-east London and Hampstead Heath and, more recently, on Wimbledon and Mitcham Commons. Such range expansion into urban areas may be due in part to changes in the management of urban parks and cemeteries”.

Clearly, in order to exist in an urban setting the Gatekeeper must have its basic requirements met by the habitat in which it finds itself. As I’ve mentioned before, the lawn in our garden is quite diverse and contains a number of native species, including a range of grasses that could be used as food plants by the caterpillars, though we do keep it quite short. It’s more likely that the caterpillars are feeding in some of our neighbouring gardens, which are rarely troubled by a mower (do neglected gardens host more biodiversity than highly managed gardens? I suppose it depends on the type of management; would be an interesting question to research).

As well as the larval food plants required by Gatekeepers, there’s a range of nectar sources available in a mixed native/introduced hedge along the northwest boundary, including the bramble I recently discussed, oval-leafed privet (Ligustrum ovalifolium), and the buddleia (Buddleja davidii var.) seen in these photographs.

It will be interesting to see if this colony persists over time (I also recorded the species in 2013 but not in 2012). I get the impression that there’s only a small number of individuals, though it’s difficult to assess the population size of butterflies without catching and marking individuals, which I plan to do next year. It’s a lovely species and we’re fortunate that it likes our garden. I’d be very interested to hear from any other urban gardeners who have seen it in their patch.

*Large White, Speckled Wood, Small White, Holly Blue, Red Admiral, Cinnabar, Large Skipper, Meadow Brown, Peacock, Gatekeeper, Comma, Brimstone, Orange Tip, Small Tortoiseshell.

Blackberry Week

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As a kid growing up in the north-east of England in the 1970s, the half-term school holiday that occurred early in October was always referred to as “Blackberry Week”. A quick on-line search suggests that the phrase goes back to at least the 1930s (can anyone trace it earlier than this?) and it refers to the time when blackberries (Rubus fruticosus agg.) were ready for picking. The local kids would spend hours at our favourite blackberry patches, picking bags full of dark, luscious berries to take home for our mothers to cook into pies and crumbles, or stewed to eat with cream. As much fruit was scoffed as was collected (“one for the bag, one for me, one for the bag, one for me…”) and over-ripe ones were pelted at one another until we looked like road casualties.

All of this has been brought to mind recently, since we began to pick blackberries in our garden – at the end of July. That’s at least two months earlier than I recall doing as a youngster. Part of this difference can be attributed to latitude; I now live more than 200 miles further south than I did, with a concomitant advance in relative dates of flowering and fruiting, amongst other phenological indicators. But that can’t be the only answer, the difference is too extreme, though I have not (and I doubt if anyone has) assessed it systematically.

The main reason for the difference, it seems to me, is that our seasons are shifting. We know that spring is generally earlier now in the UK than it was 20 years ago, and with that shift, autumn has likewise been brought forward and is lasting longer, as shown by changes in fungi fruiting patterns. There’s a lot of research interest in these changes, for example the Centre for Ecology and Hydrology’s collaborative project. Whilst phenology scientists usually express these changes quantitatively, as number of days difference between events, such as bird migration dates or plant flower times, across a period of years, any person with an interest in the natural world can see these changes for themselves, even in gardens.

Without realising it, as kids we were also making decisions about where to pick blackberries that go directly to the heart of biodiversity, which is essentially about variation and difference in the natural world. As part of our own knowledge of the local (and very personal) biodiversity of the area in which we played and explored, we would know the best bushes from which to pick fruit, and the ones to avoid because the plants produced berries that were small, or had a poor flavour. Blackberries are hugely variable in all manner of ways, including leaf shape, number and size of prickles, flower size and colour and, most importantly for us, characteristics of fruit quality.

Much of this variation is genetic rather than environmental and reflects the complex biology of the species, or should I say group of species. Let’s go back to the scientific name of blackberries: Rubus fruticosus agg. I’ve posted in the past about the formalities of writing scientific names of species, and the “agg.” element is an unusual addition not often seen. It’s an abbreviation of “aggregate”, which in its taxonomic sense means a collection of species that are very similar to, and may even be synonymous with, that species. The plant that we know and love as the blackberry is actually an aggregate of many hundreds of “microspecies”, at least according to some plant taxonomists. This is because of the variable sexual behaviour of blackberries and their tendency to hybridise.

Blackberries are often taken for granted and dismissed as invasive woodland dominators that need to be kept in check. But they are important for their cultural significance, have a fascinating biology, attract a wide range of insects to their flowers, and provide both fruit and habitat for birds and mammals. Blackberries are worth making space for if your garden is large enough.

All pollinators are equal, but some pollinators are more equal than others

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The infamous line from George Orwell’s Animal Farm asserting that “All animals are equal, but some animals are more equal than others” nicely captures an ecological view of pollinators and their relationships with plants. “Pollinators” by definition move pollen between flowers, but not all pollinators are equally good at transferring pollen of any particular plant: some are more effective than others. I’ll illustrate this with examples from the urban garden that Karin and I are developing, which I’ve discussed before.

As you can see from that link, the garden is modest in size, but nonetheless this year it contains a significant biodiversity of edible plants that require pollinators for some or all of the fruit and seed set, including: strawberries, apples, greengages, cherries, blackcurrants, squashes, courgettes, blackberries, fennel, runner beans, french beans, passion fruit, tomatoes, raspberries, and radishes.

“Radishes?!” I hear you ask. “But they are grown for their edible swollen roots which don’t require pollination!” True, usually. But we let our radishes flower because we mainly grow them for their seed pods which, picked young, are delicious in salads and stir fries, like mustardy mange tout. They look like this:

The radish flowers are pollinated by a diversity of insects including butterflies, bees, and small flies:

These insects will vary in their effectiveness as pollinators of radish, depending on the frequency of visits, how often they move between flowers, and the amount of pollen on their bodies. This last factor is largely a function of size and hairiness (bigger, hairier insects carry more pollen as a rule), though cleanliness also plays a part: insects often groom the pollen from their bodies and, in the case of bees, may pack it into their pollen baskets where it’s not available for pollination.

The size and behaviour aspect is best illustrated by some recent photos that I took of visitors to the flowers of passion fruit (Passiflora caerulea var.). We have a large, sprawling plant growing up a fence which is currently being visited by honey bees, hoverflies, solitary bees and bumblebees. In comparison to the size of the flower and the position of the anthers (male, pollen producing parts) and stigmas (female, pollen receiving parts), the hoverflies, honey bees and solitary bees are relatively small. These two images are of honey bees (Apis mellifera):

Here’s an unidentified solitary bee:

These bees were occasionally touching the anthers, mainly with their wings, so some pollen will be moved around. But from what I observed it’s likely to be a relatively small amount in comparison to bumblebees, which are usually much larger and hairier, and don’t groom themselves as often as honey bees. Here’s a Buff-tailed bumblebee (Bombus terrestris):

They were actively collecting pollen as well as nectar. Much of this pollen is packed into the pollen baskets on the rear legs and will go back to the nest to feed the developing larvae, but some will be involved in pollination:

So it seems to be the bumblebees we have to mainly thank for the deliciously sweet-sour fruit we will enjoy later in the season. Of course to test this properly we would need to set up an experiment in which we excluded larger bumblebees from the flowers and only allowed smaller bees to forage, with appropriate experimental controls. Would make a great project if any of my students are interested! But it should give you a sense of just how complex the interactions between flowers and their pollinators are: the ecology of pollination is far from simple, despite what some would have us believe.

What are YOU doing for our pollinators this year? (reduce, reuse, recycle part 6)

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Earlier this year I was asked to write a short article by my former PhD student, and still a current collaborator, Dr Sam Tarrant. Sam works for the RSPB as the CEMEX UK-funded Biodiversity Advisor, and wanted something on pollinator conservation that could be circulated in the CEMEX company’s e-newsletter. In the spirit of reworking and reusing odd bits of writing, I thought I’d post it here too.

Insects are vital for our country’s economy. Don’t believe me? Then read on….

Beneath a large black mulberry tree near the University of Northampton’s Newton Building there is a plaque that commemorates its planting “On Shakespeare Commemoration Day, 3^rd May 1916”. Despite its age this tree annually produces large crops of succulent berries, aided by the fact that wind eddies are sufficient to disperse its pollen, ensuring pollination and fruit set. Each year it’s a scramble between students, lecturers and birds, to see who can eat the most.

In contrast, the old apple trees in the grounds possess a different strategy – pollination by insects that move from flower to flower each spring. This form of pollination is both more sophisticated and less reliable than wind pollination, and is currently under considerable threat: whilst there will never be a shortage of wind currents in Britain, insect pollinators are in decline.

The apples trees are not alone in requiring insects to pollinate them, so to do other farm and garden crops, including oil seed rape, field beans, courgettes, runner beans, and strawberries and other soft fruit. It’s worth at least £440 million annually to the British economy, and most of it is done by wild bees and hoverflies, rather than managed hives of honey bees.

But all is not well with these insects in Britain – they are in decline. Although the extent of the “pollination crisis” is debated by scientists, long term records show us that these insects are under pressure: 23 species of bee and flower-visiting wasp have gone extinct since the mid 1800s, as have 18 species of butterflies. Less obviously, other species have considerably reduced in abundance so that they are now found in only a small part of their previous distribution.

There are lots of gardeners who want to “do something” for the pollinators, and keeping honey bees is often mentioned. By all means, if you wish to help the honey bees (which are suffering their own problems) then keep a hive or two. That will not, however, help our wild, native pollinators; the analogy I use is that it’s the equivalent of trying to help our declining songbirds by opening a chicken farm!

If you want to make a real difference for pollinators in your own garden, here are a few ideas:

start by planting nectar and pollen rich flowers; there’s a useful list on the Royal Horticultural Society’s website (see below).
allow plants such as clover and dandelion to flower in your lawn, bees love them.
as well as food, pollinators also need nest and egg laying sites, so you could help by allowing some of the far corners of your plot to run a little wild.
wait until late Spring to cut back hollow stemmed perennials as they are used as hibernating places by some of our bees.
allow mason bees to nest in old walls and don’t worry about them, the wall won’t fall down.
And finally, stop using pesticides!

Changing some of our gardening habits can help a group of insects on which we rely and which supports our economy in a very real way.

Further reading and information:

Bees Wasps and Ants Recording Society: http://www.bwars.com/

Bumblebee Conservation Trust: http://www.bumblebeeconservation.org.uk/

Butterfly Conservation: http://www.butterfly-conservation.org/

Hoverfly Recording Scheme: http://www.hoverfly.org.uk/

Royal Horticultural Society’s list of plants for pollinators: http://www.rhs.org.uk/Gardening/Sustainable-gardening/Plants-for-pollinators