Month: November 2016

Three trillion answers to a single question

Grantham Ecology1 Comment

On the last day of November, the decadence of summer is long gone. The flowers and leaves, butterflies and bees were so easy to take for granted until autumn and then winter take them from us. But every season has its own treasures and the wind-whipped, leaf-stripped trees are on glorious display across the countryside.

One thought which always strikes me when I see winter silhouettes, is how amazingly adept trees are at achieving their structure in an infinite number of ways. A line of trees planted together will each grow to maturity in a different form. The form will be dictated by species, by sub-species perhaps, by individual genetic variation, phenotypic plasticity to adapt to the conditions, defense responses to biotic attack or abiotic damage such as frost and wind, competition avoidance strategies and more besides. There are as many answers as there are trees to the simple question of how to be upright. And whilst the tree is growing, the process is never complete as the tree grows adaptively to maintain its balance and posture with continual interaction with their environment.

One recent 2015 study put an estimate of 3 trillion on the number of trees in the world. The mind boggles to even begin to comprehend the variety and scale which this number encompasses, but here are nine examples from my walk near Muston Meadows at dusk this evening.

2016 in Bees

Grantham Ecology1 Comment

As the winter is drawing in and the buzz of bees and other insects is sadly lacking from the soundscape of the countryside, I have put together a collection of images from throughout 2016 to remind me of warmer times!

Each photograph below is captioned with a little information about the species and the story behind it. I have learned a lot about bees and their enemies and allies this year, but it has served only to show what a vast amount more there is to learn about these vital creatures.

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This bumblebee queen was one of the first I saw in 2016 – back in April she spent the night tucked up on the bud of a bluebell. This was taken in the evening after a late-afternoon rain-shower which presumably drove her to cover. She was still there first thing the following morning, but soon took to the wing again after the sun hit the flowers.
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Blackthorn is one of those quintessential spring flowers and a local patch made a great lunchtime walk to look for early mining bees – in both the general and the specific sense as this little bee is actually called the Early Mining Bee – latin name Andrena haemorrhoa.
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This foxy little creature is another of the mining bees to appear early in the spring – this one is the Tawny Mining Bee – latin name Andrena fulva. This is quite an easy species to identify and one of the first solitary bee species I was able to ID with confidence.
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The nomad bees are a group of solitary bee species which parasitise the nests of other bees by laying their eggs in them – a behaviour known as cleptoparasitism. They are quite wasp-like in appearance and can often be found hanging around nesting burrows of the mining bees waiting for their opportunity. This one was taken at Treswell Wood, a Nottinghamshire Wildlife Trust reserve but I’m unfortunately able to identify it beyond Nomada sp.
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Like the nomad bees, this bumblebee seeks to use the nests of other bees to rear its young – however its tactics are a little more brutal. The dark wings and the lack of a pollen basket on the hind leg identified this as a cuckoo bee – this species mimics its host and then takes over the nest, killing the queen and establishing itself as the new queen. The workers then work to raise a new generation of cuckoo bees. There are several species of cuckoo bumblebee – this one is Bombus rupestris, the Hill Cuckoo Bee.
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We have red mason bees – Osmia rufa – nesting in the ‘bee hotel’ in our garden each year, but more exciting still is the ‘mud mine’ I found down at the local river Witham in Grantham. The mason bees have used this same spot for at least the last two years, arriving in good numbers to gather materials which they use to create mud-wall partitions between nest cells, and then to cap off the nest tube when they’ve finished. There is extensive evidence of their workings as many bees are taking material from here. Here you can see a mason bee with a rolled ball of mud clutched in its mandibles, ready to fly back to its nest site.
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This is another species of mason bee which I spotted in our garden for the first time this year – the much smaller blue mason bee – Osmia caerulescens. This bee spent a good period of time on our garden table in the sunshine, occasionally making short excursions to check out gaps in the construction, perhaps with a view to finding a nest site. Like the red mason bee, this species nests in holes such as dead wood and plant stems.
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This one is not a bee but one of their ‘enemies’ – an ichneumon wasp called Ephialtes manifestator. The wasp paid a visit to our bee hotel and used its long ovipositor to lay its eggs within the sealed nesting tubes within. Creating habitat for the bees will inevitably bring in the other members of the ecosystem which has developed alongside these species and the range of parasites which exploit bees is extensive!
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This tiny little bee is a harebell carpenter bee – Chelostoma campanularum. This species uses a range of native members of the harebell or campanula family, but they seemed quite excited by the ornamental campanula in our garden!
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The leafcutter bees are so named because they snip circles of leaves to create the nest cells – using it as a material in a similar way to the mud walls used by the red mason bees. They were often to be found foraging on the ornamental flowers in the garden, and can be quite aggressive to other bees, even nipping bumblebees with their leaf-cutting mandibles when they try to share their flower!
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I spend a fair few summer lunchtimes watching this colony of wool carder bees – latin name Anthidium manicatum – at the local park in Grantham. The females use the ‘wool’ shaved from plant leaves as a material for their nest tubes and furry plants like lamb’s ear are perfect for them. They also feed from the flowers of this species and so a patch of lamb’s ear is a great place for a male wool carder to hang out and wait for females to turn up. The larger males would patrol the flowers, resting occasionally on a leaf, and mate with any females who turned up. They would also aggressively chase away any other bees who strayed into their patch – larger bumblebees included – often physically grappling them off the flowers.
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I’m going to sneak these two in even though they are not bees but rather bee mimics. They are two different variants of the same hoverfly species – Volucella bombylans. The ‘bombylans‘ in the species name refers to the genus of the bumblebee ‘bombus‘. The variant on the left is mimicking the white-tailed bumblebee whilst the individual on the right is mimicking a red-tailed bumblebee. Both of these variants were photographed on the same shrub during a site survey in Cambridgeshire this summer.
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Different bees have different preferences for flowers based on their physiological characteristics – for example bees with a long tongue will use deep flowers whose nectar is further back as this is a resource unavailable to shorter tongues species (unless they snip the ends to steal the nectar but this is another matter!) The preference for flowers can also change throughout the day or the season to reflect the relative provision of different flowers which may produce more nectar at a particular time. I watched this common carder bumblebee – Bombus pascuorum – moving between different members of the pea family along the Grantham canal including meadow vetchling, tufted vetch and common vetch. It would pass by other flowers, always seeking this same family and often showing me flowers I had not spotted within the undergrowth!
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One final ‘enemy’ of the bees for this collection – I spotted this unusual looking fly skulking around on the scabious flowers in the garden where numerous bumblebee workers were foraging. It seemed to have sought out the most favourable species for these bumblebees and was waiting to attack its victim. This is a species called Sicus ferrugineus and has a particularly distasteful strategy – it lays its eggs into the bumblebee where the eggs develop, pupate and overwinter in their victim.
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I was rather taken with these little heather colletes bees – Colletes succinctus – this year. We came across them whilst walking in the peak district in September when the heather was in full flower. After spotting them foraging as we walked, we began to come across aggregations of holes in the sandy soil of the paths which were the nest holes of this species and a little patience allowed us to watch them coming and going. They appear late in the season, to coincide with the vast abundance of heather flowers in these habitats.
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A September walk in Slad revealed these little Lassioglossum sp. bees on many of the grassland flowers – scabious seemed a favoured food source but they were also using ragwort and others. They are such characterful little bees especially when you catch them face-on with their long antennae.
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Into November, the queen bumblebees began to appear again. These queens will overwinter to set up next year’s nests in the springtime. The density of flowers in the wider countryside decreases significantly as the season turns to winter, but ornamental species such as these naturalised Michealmas daisy can be an excellent late-season nectar source for queen bumblebees, especially on a sunny afternoon.
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Perhaps my favourite bee photo of 2016 – this bumblebee feeding on Verbena in my parents’ garden during their Open Garden event this year.

Hornet Sentries

Grantham Ecology2 Comments

I was intrigued to spot the nest of an European hornet – Vespa crabro – in an old haybale at a survey site recently. It was the middle of October and the weather was turning cooler and damper.

I was fascinated by the behaviour of the guards who were stationed at the entrance where hornets returning to the nest would land and enter. One individual was stationed to intercept each new arrival, touching antennae with them before either letting them pass or subjecting them to further scrutiny.

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A hornet sentry stationed at the entrance to a nest built into an old hay bale

I can find little on this behaviour in hornets, but as a social hymenoptera, I hope that honeybees are a good parallel. The seminal piece on guard behaviour seems to be Butler and Free’s 1952 paper entitled The Behaviour of Worker Honeybees at the Hive Entrance.

In honeybees, the guards are drawn primarily from younger bees with older workers rarely taking the role. The role of guard is also not fixed – many also forage and will even be seen attempting to rob the nests of other hives. If the hornet system is the same, this would mean that one of many workers can take the sentry role.

In the paper, the Guard Bees are described as ‘assuming a very typical attitude, frequently standing with their forelegs off the ground, with their antennae held forwards and their mandibles and wings closed. Should they become even more excited they open their mandibles and wings and appear to be all ready to rush towards any intruder. Such excited guard bees watch the movements of bees flying overhead and approaching the hive, often jerking round to do so, and make intention movements to intercept any bee which they see to alight near them‘. This very neatly describes the behaviour I was watching, and is shown in the photograph below of the guard intercepting a new arrival.

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The hornet sentry waiting to interrogate a new arrival on their return to the nest

The method of interrogation was through contact between the antennae of the two hornets – social hymenoptera have an advanced ability to distinguish between those within their colony and those outside – termed ‘kin recognition’. Some individuals returning to the nest showed almost no signs of interest in the guard and simply barged on in whilst others paused and interacted with the guard before being allowed entry.

The guard did their best to check their credentials and usually found them acceptable, but sometimes would follow a returning hornet into the entrance for further investigation.

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Showing the guard hornet interrogating their nestmate

One or two individual hornets were not permitted entry, despite repeated attempts to gain it. They would be chased away across the face of the haybale by the guard, soon to return and re-attempt entry only to be denied once more. There may be several reasons for this. These rogue hornets could be individuals from another nest, or it could be that the guard was mistaken in denying entry to a member of their own colony. The system relies upon chemical signals, and is not perfect leading to errors through denying entry to legitimate colony members as well as sometimes accidentally allowing entry to non-nestmates.

The investigation in honeybees noted that intruders carrying a load of pollen were usually permitted entry whilst those without were more likely to be intercepted and turned away. This is perhaps on the assumption that robbers rarely come bearing gifts and so their arrival with resource suggests they can be allowed in. Other factors important in influencing guard behaviour was recent disturbance – if the nest was disturbed and the bees felt under threat, they were much more likely to examine newcomers, even those with a full load of pollen.

This is a fascinating fascet of behaviour and I have tried to piece together the likely story based on the research into the honey bee. If anybody can provide me with further information about this behaviour in hornets, I would love to hear from you!

A November Walk in the Quantocks

Grantham Ecology2 Comments

Sometimes surveys take me further from home, and a Monday morning survey in Somerset invited an early start to take advantage of the opportunity to explore somewhere new. A chance leaf through the Guardian Travel’s Best Autumn Walks section on Sunday night obliged me with an excellent suggestion – a walk from Adscombe across the Quantock hills to Crowcombe and back.

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The drive on the approach to Crowcombe presented this autumnal treat – it’s difficult to get over how beautiful beech trees look in their yellows and golds. The beech is generally considered native only towards the south of Englan, and whilst there are plenty of specimens tp be seen around the Midlands, it’s only really on a trip south that you can really enjoy their autumn exhuberance en masse.

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There must be a name for when something inanimate catches your eye and morphs into something alien. When I was on a field site at uni, I remember we watched a hare stock-still in the woods for a good 5 minutes before realising it was an apt arrangement of log and stick. This piece of branch and moss caught through the wire fence at the beginning of the walk put me in mind of a tiny maurauder breaking through the defences, strangely sinister!

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The walk took me up through Great Wood, managed by the Forestry Commission. The woodland is varied – from dull conifer plantation to glorious semi-natural oak woodland, all punctuated by beech boundaries where the roots pour over the tops of the banks as the trees cling to their precarious looking anchor points. This smartly-spaced plantation of conifers caught my eye, especially the way the light increases as the beech re-asserts itself on the banks which rise up behind.

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There were plenty of mushrooms and fungi to be seen in the woods – this was a particuarly impressive ring around a conifer. I’m not sure on the species but would welcome enlightenment!

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The route I took went close to Dead Woman’s Ditch, and passed through this spectacuarly gnarled sessile oak woodland. These trees are of a considerable age, but the poor quality of the soils and the exposure results in them being relativly small and encourages these gnarled, twisted growth forms. These are ancient woodland sites, many of which had uses for charcoal and tanning in the past. These days, they provide excellent roosts for a range of bat species including rare barbastelle and Bechstein bats.

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The walk back up from Adescombe took me up Quantock Combe – this is the name given to a steep narrow vally which cuts down the hillsides. The stream running through this combe was gentle and shallow, crossable at almost all points, and overshadowed by ferns and bracken.

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Back up to the top once more, I crossed a cow-grazed pasture to reach the Drove Road which took me back towards Crowcombe. This beech-lined trackway has the gnarled roots replacing the rocks in the walls in places, and provides a sheltered passage across the open fields. Sadly, the exposure meant most of the autumn leaves had already been consigned to the wind, but it must be glorious in its peak. This track is probably pre-historic and was once an important trading route. The sunken track bears testimony to centuries of footfalls, which is a truly humbling thought.

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Before the descent back into Crowcombe, I walked up to Beacon Hill to take in the view from the trig point. Here, the scenery changes from the lushious woodlands to a blasted heath with gorse, heather and Deschampsia with the flar agricultural plains stretching out below.

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Despite being well into the middle of November, there were plenty of flowers to be seen along the route including red campion, bramble, gorse, dandelion, herb robert, wood sage, hedge woundwort and heather.

There are many tracks between Crowcombe and Adscombe, meaning there is no need to retrace your steps on a circular walk between the two. The route I took was a pleasant 8 1/2 miles with some good ascents and descents (certainly compared with my neck of the Midlands!). Allow a few hours to meander and explore, there’s plenty to distract you along the way!