Wednesday, November 20, 2013

The Industrial Revolution in Reverse - Steam gives way to Water Power

Thursday's Guardian Country Diary describes an unusual piece of industrial archaeology in a remote Northumbrian valley.

This is the sight that greets you when you follow the track down from the delightfully-named Pennypie cottage towards Blanchland, at the mining hamlet of Shildon (not to be confused with the town of Shildon in County Durham) which is a mile north of Blanchland. All that's left of this community, that in its heyday numbered over 150 people, is a couple of cottages and this old engine house, together with some mine shafts in the hillside.

The engine house was built in 1806 by mine owner John Skottowe, to house a Boulton and Watt steam engine that was built to pump water from the underground lead mine shafts and tunnels. Waterwheel-driven pumps were no longer up to the job so he imported the latest technology from the tin mines of Cornwall.  A contemporary account describes how 'a steam-engine of great power was erected, the cyclinedr being of 64 inches in diameter, and the main beam weighing upwards of nine tons'.

It should have solved Skottows' problems especially as he owned coal mines across the border in County Durham, but the steam engine turned out to be uneconomic and he reverted to waterwheel driven pumps, dismantling the steam engine and transporting it to Backworth colliery. There was no rail access to Blanchland when the mine engine was installed and even when a rail link did arrived (in 1834) the line ended at Parkhead, five miles away.

The likely reason why steam-driven pumping was abandoned is that this little valley is so remote Even today the roads quickly become treacherous after a snow fall and two centuries ago, when they were less well maintained and horses and carts were used, they must often have been impassible in winter. 

After the steam engine was removed the building was converted to miners' accommodation, with the addition of three floors inside, and it became known locally as 'Shildon Castle'. The mine went into decline, unable to compete with imported lead, and many of the miners emigrated - you can read fascinating accounts of some of them by clicking here

This is the slit in the wall where the beam of the steam engine would have rocked up and down. At the top of the slit you can see the fireplaces that were installed when the building was converted to workers' flats.

You can see more photographs of the site, before its recent restoration, by clicking here

There was a vigorous exchange of mine workers and mining technologies between Cornwall and Northumberland in the early 19th. century, which you can read about by clicking here

You can download a useful pdf guide to the geology and landscape around Blanchland by clicking here

You can download a detailed report on Blanchland and its surround area by clicking here

Sunday, November 17, 2013

The Itinerant Flora of a City

Every year the cityscape of Newcastle changes, as old buildings are demolished and the legacy of polluting industries from the past is cleared away. This site is in the Lower Ouseburn valley, once the location of a devil's caudron of industrial pollution but soon to become the site of 76 energy efficient 'green' homes. 

The patch of land in this picture has been derelict for several years - just a pile of broken bricks and earth bulldozed and then left, so that temporary colonisers took over.

Two years after the land was bulldozed, in the summer of 2011, it hosted the finest display of dyers rocket aka weld Reseda luteola that I've ever seen.

The site was so densely covered with this bee-friendly biennial that I wondered whether it might be the legacy of these plants being used in dye production in the 19th. century; in his New Naturalist book Weeds and Aliens Sir Edward Salisbury suggests that the plant's abundance and distribution often suggests that large populations are relicts of the plants' former cultivation. They have a vast seed output (Salisbury quotes up to 76,000 seeds per plant) and it's possible that the seed could have remained dormant for many decades.

There was also a good display of corn poppies amongst this temporary urban field of wild flowers. Their seeds germinate in even the smallest area of waste ground in Newcastle when they are brought to the surface by soil disturbance and exposed to light and moisture. 

Now that the site has been levelled and the rubble taken away, these plants will be on the move again - carried as seeds in rock, bricks and soil that have been taken away and probably used at another site in another part of Newcastle - part of the itinerant flora of the city.

Wednesday, November 13, 2013

Nectar in November

Insect numbers have plummeted since the first hard frosts arrived about a week ago, but ivy provides an almost unlimited supply of food for those few that are still active. The flowers continue to open well into December, although many of them will never be pollinated and produce berries. 

The first ivy flowers that open in September are almost all pollinated and produce berries that ripen in March, like those on the right of the picture above, whereas those that open after the first frosts, after insect numbers decline, are much less likely to be fruitful - like those on the left in the image above.

If you take a close look at ivy flowers on humid autumn mornings you can see the glistening drops of nectar on the surface of the exposed nectary ....

.... that are easily accessible to all insect visitors, including this small fly - one of the few insects that's still active. Although it can reach the nectar reward it doesn't make effective contact with the stamens and isn't well equipped with body hairs to transport pollen to that stubby stigma in the centre of the flower.

A few years ago observations on the vast range of insects that visit ivy flowers - including bees, wasps, flies and butterflies - prompted a group of researchers to investigate which of these was the most effective pollinator (see details of source publication at the end of this post). 

This is an ecologically interesting question because successful pollination in autumn leads to prolifically berry production in spring, providing an important food resource for migratory birds at a time when they need it most. The survival of some berry-eating birds in spring could hinge on the performance of insect pollinators of ivy in the previous autumn 

The researchers found that the most effective ivy pollinators were wasps. 

You can see here that a wasp is more hairy than is often supposed and it's just the right size to collect pollen as it feeds. It acts as a brush, picking up pollen and distributing it was it crawls across the flower surface, indulging in its taste for sweet nectar. 

So maybe we should rethink our attitude to those pesky, drowsy wasps that can be a painful nuisance once they abandon their nests in autumn and set out in search of anything sweet. Their late-season activity may well be playing a significant role in the lives of migratory birds..........

Source: Jacobs, J.H., Clark, S., Denholm, I., Goulson, D., Stoate, C. And Osborne, J.L. (2010).  Pollinator effectiveness and fruit set in common ivy, Hedera helix (Araliaceae). Arthropod-Plant Interactions 4 (1), 19-28.

For more on wasps, click here.

Wednesday, November 6, 2013

No ladybirds for months, then five species all at once.....

Thursday's Guardian Country Diary describes encounters with ladybirds in Weardale and Teesdale.

Back in the spring it seemed as though 2013 might be a good year for ladybirds locally - plenty of 7-spots seemed to have come out of hibernation so I anticipated a thriving population by the time their offspring hatched in summer - but it never seemed to materialise. I found a few isolated individuals of other species - notably 22-spot , 14-spot and an orange ladybird  but then last week .........

........ this huddle, near a pine plantation at Wolsingham in Weardale. It was the largest number of 7-spots I'd seen in one place all year: six that had chosen a split in a fence post as their hibernation site. 7-spot ladybirds aren't usually associated with conifer plantations but his particular row of fence posts, on the sheltered, south facing side of the plantation, as always been a good place to find other species

So it was no surprise to find this eyed ladybird - a conifer specialist - sunning itself on the same line of fence posts.

A small, unidentified fly with unusual up-turned antennae had even chosen to hitch a ride on it. The eyed ladybird is our largest species but ...

...... this one, a larch ladybird that shared the same fence post, is one of our smaller species ...

..... here going head-to-head with a staphylinid beetle (which it simply head-butted out of the way!)

Then, a day later at Egglestone in Teesdale I found ivy in full flower that had attracted several orange ladybirds, that were feeding on nectar.

You can see here the translucent pronotum of this species, that used to be considered scarce but seems to have increased in abundance in recent decades, supposedly because it has taken to feeding on fungi that grow on the honeydew secreted by sycamore aphids. On one occasion a few years ago I found a cluster of ten of this species hibernating on the bark of a sycamore in winter - it's certainly a species that can be added to the very small number of insects that are associated with sycamore, which has been present on these islands for around 500 years but has a very small insect fauna.

Close to the orange ladybirds on the ivy I then found a single 7-spot sunning itself on a fence post and ......

.......... scores of this very unwelcome addition to our ladybird fauna - the harlequin. The first time I saw these locally was in Durham city back in 2009, on ivy flowers at almost exactly this time of year. Harlequins are noted for their bewildering range of colour patterns but the indentations at the tail end of the elytra are also a distinctive feature, although they too vary in extent between individuals.

This group of about a dozen individuals had just hatched from their pupae and were still developing their full colours. Harlequins have a breeding season that extends well into autumn.

Some, that also seemed to be the most rotund individuals, were almost entirely black ...

..... but his was a more typical colour pattern in this population.

Finding another population of harlequins was an unwelcome discovery because this disease-resistant species is known to be a predator of our native ladybirds and can also transmit a parasite that kills other species. It also feeds extensively on eggs of butterflies and moths. Over the last decade it has spread rapidly from south east England to the Scottish border. It originated in central Asia but was introduced elsewhere in misconceived biological control programmes aimed at 'environmentally friendly' aphid control in greenhouse crops. Wherever it has been introduced it has escaped and has had a detrimental effect on native insect populations.

The predominantly black individuals seem to have blue eyes.

This was the last unhatched pupa, attached to the fence posts. At the point of attachment you can just see the remains of the larval skin, which is spiny in this species. 

Harlequin larvae also seem to have an affinity with sycamore, perhaps because of the vast supply of sycamore aphids that they find on the leaves - so it may well be that orange ladybirds will also form part of their diet too.

If you find harlequin ladybirds you can report their presence by contributing the record to the Harlequin Ladybird web site.

Saturday, November 2, 2013

Grow-your-own wild bird food

Time to start feeding the birds again, which must be even more satisfying if you grow your own sunflower seed for feeding finches..............  

I noticed these magnificent giant sunflower seed heads drying in a garden at Blanchland yesterday. Made me wish I'd grown some too. 

Next year.....................