Ferns

I have been writing a short piece in the Grantham Canal Society newsletter each month for the last three years – I thought it would be fun to share these little snippets on here! If you would like to subscribe to the digital newsletter which drops into your inbox once a month, or look at older issues, visit their website here:

February 2018 – Ferns

At a time of year when many wild plants have lost their green leaves, ferns can still be found brightening up bare walls. Those you are most likely to spot along the Canal are perhaps the Aspleniaceae, known by the common collective name of ‘spleenworts’. These species often grow in cracks in walls, where they find small patches of soil, and they like moist and shady conditions. These factors together make some of the walls along the canal, particularly around the locks, ideal habitats.

One of the most common and easily recognisable is the hart’s tongue fern – this is quite distinctive in that it is the only fern you’ll come across which has undivided leaves, looking more like a ‘normal’ plant but given away by its glossy leaves with spores dotting the undersides.

Another common species is the maidenhair spleenwort, which has a glossy, dark frond stalk and neat green leaflets arrayed on either side. Black spleenwort too is a common wall resident which looks more like fronds of your ‘typical’ fern or bracken.

These ferns are different to most of the other plants you will see along the canal – they neither flower nor produce seed but instead reproduce by means of spores which are lined beneath the leaves. The name ‘wort’ after a plant usually means that it was a food, or used medicinally. It is thought that the name spleenwort derives from folk beliefs that the plants were useful in curing afflictions of this organ!

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Maidenhair Spleenwort – Asplenium trichomanes

Kingfishers

I have been writing a short piece in the Grantham Canal Society newsletter each month for the last three years – I thought it would be fun to share these little snippets on here! If you would like to subscribe to the digital newsletter which drops into your inbox once a month, or look at older issues, visit their website here:

February 2017 – Kingfishers

If the weather is mild, then February is the month in which kingfishers will begin their courtship. Kingfishers lead a solitary existence in the winter – catching their prey can be hard as high water, poor visibility and the tendency of fish to move into deeper water all make fishing difficult. For this reason, a kingfisher will hold their own territory, often including waters not frequented in the summer, in order to maximise their chances of survival.

Once the first signs of spring begin to appear, pairs will court and share a territory once more, ready for the breeding season ahead. Kingfishers typically excavate nest tunnels in vertical banks, digging back 60-90cm and laying a clutch of eggs at the end. Through the summer, the pair can raise 2-3 brooks in quick succession, spending little time with the young once they have fledged in their haste to start the next clutch.

February and March are excellent times to spot kingfishers along the canal – the process of forming pairs and negotiating territories makes them active and vocal. All this whilst the leaves are yet to burst on the trees makes it easy to see that flash of electric blue zipping low along the water. If you’re trying to spot them on the banks, look on overhanging branches and think of their orange-brown chests as well as the typical blue of the backs – if they are facing towards you then this is what you need your eye in for!

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Wild Clematis

I have been writing a short piece in the Grantham Canal Society newsletter each month for the last three years – I thought it would be fun to share these little snippets on here! If you would like to subscribe to the digital newsletter which drops into your inbox once a month, or look at older issues, visit their website here:

January 2020 – Wild Clematis

In the hedgerows and trees along the canal in winter time, you might be lucky enough to spot the silken seedheads of wild clematis, also known as ‘travellers joy’ or ‘old man’s beard’ The small dark seeds are clustered in the centre whilst the white fluff which surrounds them are feathery wings which allow the seeds to catch the breeze and reach a new location. Many seeds will inevitably fall in unsuitable places, but through probability and strength in numbers, some will find a suitable place to germinate and develop a new plant. Wild clematis is a liana – a long-stemmed, woody vine – alongside other familiar species such as honeysuckle and grape vines. It can persist scrambling though herbaceous vegetation, but is most at home clambering up supports such as trees and shrubs where it twines around its unfortunate host.

Wild clematis has the latin name Clematis vitalba and is actually a member of the buttercup family. At this time of year, the seedheads provide a good source of food for wild birds such as goldfinches, whilst the flowers which preceded them sustained bees, butterflies and moths. Several species of moth are completely dependent on this species as a larval food plant, including the Small Emerald, the Small Waved Umber and Haworth’s Pug.

The native clematis is related to the garden varieties which people may be more familiar with – the flowers from July to September are less exuberant than their ornamental cousins but they share the same vanilla scent.

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Wild clematis seeds

Long tailed tits

I have been writing a short piece in the Grantham Canal Society newsletter each month for the last three years – I thought it would be fun to share these little snippets on here! If you would like to subscribe to the digital newsletter which drops into your inbox once a month, or look at older issues, visit their website here:

January 2018 – Long tailed tits

A walk down the towpath in January is likely to be accompanied by the flutter of wings and warning calls as birds forage in the path-side hedgerows. One of the smallest species in the UK is likely to be among them, but far from being discreet they make their presence disproportionately known as they forage.

Long tailed tits, weighing just 9g, are highly social birds – they move through the landscape in flocks of closely related individuals, maintaining a shrill ‘si-si-si’ call-and-response as individuals keep in touch. Their aim, at this time of year especially, is to forage for enough high-value food to keep their tiny bodies warm enough to survive. They seek invertebrate prey by preference, capitalising on their low weight to pick food such as moth eggs as well as other invertebrates from the higher reaches of twigs and leaves which their heavier counterparts are unable to reach.

At night, the flock remains together, nestling down in a shrub or tree to form a dense ball with just their tails sticking out. As spring marches on, they will be building their tiny nests out of moss, lichen and spiders webs, lined with feathers. Interestingly, they are also social at nesting time – they will try to pair up and nest on their own but if unsuccessful, they will help at the nest of a close relative.

Listen out as you walk this winter – the distinctive call will alert you to the presence of these charming little ‘flying teaspoons’!

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Long tailed tit on hawthorn – image kindly provided by Ryan Clark

Fieldfares

I have been writing a short piece in the Grantham Canal Society newsletter each month for the last three years – I thought it would be fun to share these little snippets on here! If you would like to subscribe to the digital newsletter which drops into your inbox once a month, or look at older issues, visit their website here:

January 2016 – Fieldfares

Fieldfares and redwings are two thrush species which arrive in the UK for the winter each year, having spent the summer in their breeding grounds in Central Europe. The UK has had unusually mild conditions this year which has led to lower numbers than usual, but October and November still saw a good influx.

The Grantham Canal is always a reliable place to find chattering flocks of fieldfares which work their way along the hedgerows in search of the dogrose hips, hawthorn haws and blackthorn sloes, as well as the less obvious ivy berries which form a vital part of their diet in January and February when the best of the berries have been stripped. Their diet also includes insects, fruits and grains.

They are often quite cautious of human presence and their distinctive flight-call – a harsh “tsak tsak tsuk” – will often signal them moving ahead of you along the towpath.

Fieldfares and redwings often fly in mixed flocks but are easily told apart. Redwings are a rich warm brown with rusty-red underwings – similar in size to a song thrush – with a bold white line across the eyebrow. Fieldfares have more white/grey colour about their bodies and are slightly larger – similar in size to a blackbird. They lack the bold red underwing and the black supercilium which distinguish the redwing.

Both of these winter thrushes tend to stay with us through until April or early May when they head back to their breeding territories in warmer climes.

Fieldfare feeding on cotoneaster berry
Fieldfare feeding on cotoneaster berries

Christmas Special – Mistletoe

Along with the holly and the ivy, mistletoe is one of those species which is intimately associated with the festive season. You might almost say it is a hemi-parasite on the cultural Christmas tree…

A small group of us undertook some voluntary tree climb surveys in Clumber Park before Christmas 2018 to look for roosting bats. One of the  trees which I climbed was an old lime set amongst younger trees and this had some beautiful examples of mistletoe right in the top of the crown. It seemed a good opportunity to share some photos and ecological insights into this fascinating plant.

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The lime tree holdings its territory against the younger tree stock crowding around – the mistletoe is visible at the top of the tree

Mistletoe is a obligate hemi-parasite – it is only found growing attached to trees. This is because it is partially reliant on the tree for sustenance – it taps into the xylem system of the tree to source water and soil minerals. It does however phytosynthesise itself which makes it only a half or partial (hemi) rather than full parasite.

Mistletoe does not have roots, rather it grows on the surface of the branch and encourages the tree to grow around it. This gives the illusion of it penetrating the bark to reach into the branch and take its sustenance, but the truth is much less aggressive.

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A new mistletoe sprig establishing at the top of the lime tree

The main ‘mistletoe’ heartland in the UK is the south-west midlands – this is particularly around Herefordshire, Somerset, Monmouthshire and Gloucestershire and up as far as Warwickshire. It is however found sporadically in many other locations around the country – close to Grantham, the village of Bottesford seems to be unusually well covered. The origins of these more isolated pockets of mistletoe is often unclear, but many old parklands and country estates tried to establish colonies in the past and it may be that these give rise to local populations away from their stronghold. Given the history of Clumber, this might be a good explanation for the colony I found!

Mistletoe expresses a significant preference for some tree species over others – cultivated apple is the most well-recorded host with lime (like the Clumber tree) coming in second. Other species include hawthorn, poplar, maple, and willow. They have however been recorded on hundreds of tree hosts and some have particular cultural significance – mistletoe growing on oak was the centrepiece of a Celtic religious ceremony.

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Mistletoe berries like pearls amongst the leaves – although these look ripe, they won’t in fact be ready until the early springtime

Most fruit and berry-bearing species in the UK owe a debt to wild birds who disperse the seeds, but mistletoe has a particular reliance upon them. Some species, such as the aptly named mistle thrush, will eat the seeds and excrete them again – often whilst perched on a branch. Not only does this deliver the berries right to the branches but it comes with its own ‘glue’ in the form of the droppings, to help hold the seed in place whilst they develop. Other species such as blackcap wipe the seeds from their beak directly onto the tree – a cleaning action which is coincidentally very likely to deliver the seed to an ideal spot for germination.

This means of spreading seed is the reason for the common name of mistletoe – ‘mistle’ derives from the Anglo-Saxon word for dung and ‘tan’ derives from the word for twigs. The latin is Viscum album – the album meaning ‘white’ and relating to the colour of the berries.

Small patches of mistletoe often go un-noticed or overlooked – either because it is concealed by the dense leaf cover of its host tree, or because people are simply not looking up and around to spot it. Winter is an ideal time to spot this fascinating species – keep your eyes skywards and look out for the characteristic globes of vegetation suspended bauble-like in the branches!

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Mistletoe high in the lime tree in the late afternoon sunlight

If you want to find out more about mistletoe – its ecology, natural history, cultural significance, distribution and commercial importance – I would highly recommend reading Jonathan Briggs’ Mistletoe Diary blog!

 

 

Thermal Imaging footage of Honeybees and Bumblebees

Thermal imaging technology works by recording the infra-red energy emitted from surfaces – this doesn’t rely on a light source like typical infra-red photography, but instead measures the radiation given off by both living an inanimate objects. The camera can measure the temperature of these items and display a ‘thermal’ image which shows the gradation and variation between different objects within the field of view. In simple terms – it can show a hot object as white/red whilst cooler objects would be shown as green or blue.

In mid-summer, social bees produce a high density of very busy insects in the nest, so it was no surprise that they stand out a mile on a thermal camera! It was also exciting to be able to understand what individual bees had been doing – for example their temperature signature differentiated those who had recently returned to the nest from those who were standing guard and checking in new arrivals.

Wild Honey Bee Nest

We often encounter honey bees when out looking for tree roosting bats in woodland and this was a prime example! Whilst honey bees are often kept in hives, they can establish wild colonies in features such as this.

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Showing the tree cavity feature where the honey bee nest was located

I took the following images around sunset so the tree itself was cooling but you can immediately see just how hot the inside of this tree cavity is compared with the surrounding wood. The temperature reading inside the nest was 33 degrees Celsius, whilst the surrounding tree barn dropped to around 25 degrees.

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A still photograph of the bees within the nest – you can see the differential in heat between the nest itself (yellow) and the outer wood (black). You can also see a recently-returned bee glowing white hot!

Even at sunset, honey bee workers were still returning to the nest and you can see the white-hot glow of these warmer bees compared with the much cooler bees at the entrance. What is also interesting is the pattern of heat in these recently-flown bees – the flight muscles are in the thorax where the wings are attached and this part is much hotter than the abdomen as you can see more clearly in the video below.

The thermal image gave a nice opportunity to watch guard behaviour in action – some honey bees will take the roll of guarding the nest entrance, positioning themselves on the edge and checking returning bees to ensure that they are welcome. The thermal footage clearly differentiates those bees who have recently flown from those which have not, and you can see the much cooler guard bees intercepting the warmer returning workers as they pass by.

If you’re interested in guard behaviour, you might also like this post from a couple of years ago regarding this behaviour in hornets!

Bumblebee Nest

These images and videos come from a bumblebee nest which was situated underneath a loose cobble in the courtyard of our office.

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The stone beneath which the bumblebee nest is situated

I think the bumblebees are either white-tailed (Bombus lucorum) or buff-tailed (Bombus terrestris) bumblebees – this photo shows one of the worker bees returning with well laden pollen baskets.

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Bumblebee worker returning to the nest with well-laden pollen baskets.

The thing that I found most surprising on the thermal footage to see just how hot this cobble got compared with those around it, even though the nest is buried beneath! I assume this is due to the heat rising with the warm air from the next and heating the stone as it passed by.

As with the honey bees, you can see how much warmer the active bumblebees are compared with their environment. Bumblebees have a good degree of control over their temperature. The hairs on their body provide some insulation and they can use their flight muscles – uncoupled temporarily from their wings – to warm themselves up before taking off. This uses the same technique as they use for buzz-pollination of some flowers. This video gives an idea of just how much heat these muscles can generate, allowing some bumblebees to remain active through the winter, flying at temperatures of just 10 degrees Celcius. You can read more about bumblebee thermoregulation here!