Monday, August 30, 2010

Exotic Tastes

Wasps tend to turn their attention to satisfying their urge for anything sweet at this time of year and in my garden the red-hot pokers (Kniphofia spp.) are proving irrestistible to them. Red-hot pokers are pollinated by sunbirds in their native South Africa and to satisfy these birds' energy needs they secrete large volumes of nectar. Wasps (Vespula vulgaris) are so desperate to reach it that they even try to get at the nectar in the unopened florets, as this one is doing, by chewing through the flower's corolla - you can see where it's already tried to chew a hole in the floret immediately above it, then gave up and having a go at this one instead.  

As soon as the florets at the bottom of the inflorescence open the wasps force their way into the narrow tube, which evolved to accommodate a sunbird's slender, curved beak. The wasps have to bend their forelegs backwards to reach the drops of nectar at the top of the tube (you can see the foreleg bent back, just above the wing, in this photo). It's even more of a struggle for them to get out.

Sunday, August 22, 2010

Badly-Behaved Botanical Tourist

A great deal has been written about alien plant species like Japanese knotweed and Himalayan balsam, that have spread into our countryside and proved difficult to control, but inter-continental movement of plant species is two-way traffic and many British wild flowers that are perfectly well behaved here have proved to be devastating invaders when they've been exported overseas. Few have had a greater impact than purple loosestrife Lythrum salicaria, which was introduced into North America in the early 19th. century and has since choked native vegetation in wetlands over a wide area, proving difficult and expensive to control. Here in the UK it's a valued component of the emergent vegetation of wetlands and a desirable plant for a wildlife garden. Back in 1999 a study of 25 wild flower species at Cambridge University Botanic Garden found that it was the best of the bunch for attracting butterflies, and the purple loosestrife in my garden attracts a constant stream of insect visitors like this bumblebee, that was foraging on its flower spikes this afternoon.

Wednesday, August 18, 2010

It Pays to Advertise

Guelder rose's berries are ripening and its leaves are taking on their autumn colours already. The berries are so shiny that they look permamently wet.

Back in the early summer I photographed this same plant, in a hedgerow in Durham, when it was in flower and you can see one of the peculiarities of its blooms - two kinds of flowers in each inflorescence. Only the outer ring of flowers have fully developed petals but they are there purely to provide a long-lasting advertisement to visiting insects - they're sterile and they don't produce any fruits.

It's only the small, petal-less flowers in the centre of the inflorescence that have stamens and stigmas and ultimately produce the berries. The fine crop of fruits currently ripening shows that the arrangement works. Garden hydrangeas have a similar floral division of labour in their inflorescences.

Tuesday, August 10, 2010

The Price of Success

I photographed this grey squirrel on Wimbledon Common on Sunday, where it was scavenging picnic leftovers and delighting young children with its antics.

People have strong opinions about grey squirrels. There are some, who refer to them as grey ‘tree rats’, who would like to see them exterminated in Britain ……………… but back at the end of the nineteenth century there were plenty of landowners who had the same attitude towards native red ‘tree rats’. In 1903 the Highland Squirrel Club was formed  and over the next 30 years killed 85,000 red squirrels in an attempt to protect their forests from what was then seen as a pest. Earlier still, in the 1830s, 20,000 red sqirrels were sold annually by butchers in Leadenhall and Newgate markets in London, anticipating today's growing trade in grey squirrel meat.

I guess there’s a lesson in there somewhere – that it doesn’t pay any wildlife in Britain – native or introduced – to be too successful. Himalayan balsam, Canada geese, ring-necked parakeets, ruddy ducks, sparrowhawks, ivy, foxes, magpies and even peregrine falcons, red kites and sea eagles – to name but a few – have all become the focus of wildlife zealots because they are just too successful. I can see the sense in defending remaining strongholds of red squirrels against their grey counterparts, but elsewhere it seems pointless to expend resources on killing them at the same time as our affluent, effluent society provides them with virtually unlimited food resources in our garbage.

Maybe the lesson for grey squirrels is to adopt a lower profile - as this one seemed to be doing......

Wednesday, August 4, 2010

Well-travelled Weed

If you happen to be standing in a farm gateway and detect a whiff of pineapple scent in the air, this is where it will most probably be coming from - the rayless mayweed, also more aptly named pineapple weed, Matricaria discoidea. No one is quite certain where it originally came from or how it arrived in Britain but it probably came here from the North-West United States, and it may have reached there from North-East Asia, where it also grows. Since it first appeared here, in North Wales in 1871, it has spread to every part of the UK.

Pineapple weed thrives in compacted soils that few other plants will tolerate and is often found in farm gateways - and almost anywhere where soil is compacted by the weight of vehicles. Sir Edward Salisbury, the late Director of the Royal Botanic garden at Kew and author of the the New Naturalist classic 'Weeds and Alien's (1961) attributed pineapple weed's success to two factors - aside from its tolerance of soil conditions that deter competitors. One was its prolific seed output. Salisbury was a meticulous measurer of weeds' reproductive potential and calculated that, on average, the plants produce about 7000 seeds, 93% of which germinated. He found one exceptional plant that produced an estimated 70,000 seeds. The second factor was the motor car. Pineapple weed didn't really begin to spread far and wide until widespread ownership of cars with treaded tyres carried the seeds in mud over long distances; pineapple weed is a botanical hitch-hiker.

Tuesday, August 3, 2010

Comma in a Cornfield

I found this comma sunning itself on the edge of a field of ripening wheat yesterday. It's a common enough butterfly now in Durham but twenty years ago it was still a rare sight here. As recently as 1986 T.C.Dunn and J.D. Parrack wrote in their Moths and Butterflies of Northumberland and Durham that occasional specimens that were reported were "...only strays and cannot yet be thought of as recolonising the north-east, although there is recent evidence of some range expansion in the Midlands. They are, however, an indication that they do arrive here sometimes and if the wandering habit were to become more frequent as during a time of expansion, it could take up residence here once more". The authors would be delighted, I sure, to know that their predictions proved to be spot-on. The species went into a decline nationally in the late nineteenth and early twentieth century, when it was restricted to the Welsh Borders and South East England, but over the last few decades it's undergone a rapid range expansion. No one seems certain why this has come about, although there are suspicions that this is now a different race of butterfly than that which was common 200 years ago, with caterpillars that now feed on nettles rather than the much less common hops. Climate change might have asisted its northwards range expansion too.

This specimen looks like an example of the paler form from the first, July, brood known as form hutchinsonii, which will mate and produce a second brood in late August. The larger, darker form in the July brood merely feeds without mating and enters hibernation along with the second brood hutchinsonii progeny.

Sunday, August 1, 2010

Islands in the Stream

Now, I have to concede that this site of industrial dereliction might not look like a good place to spend a morning communing with nature, but it has its charms. This is the Ouseburn, a tributory of the Tyne that flows into the river about a kilometer downstream from the Tyne Bridge in Newcastle. In the nineteenth and early twentieth centuries this was the location of some of the most polluting industries imaginable: lead smelting works, potteries, iron foundries, flax spinning mills, holding pens for imported cattle, surrounded by slum housing and all discharging effluent into the tidal Ouseburn. Part of the Ouseburn Valley was filled in with noxious industrial waste and the tip sometimes spontaneously combusted during hot summers. Slum clearance and industrial decline left it as a site of dereliction until serious regeneration of the lower Ouseburn valley began in the late twentieth century. Old warehouses have become artists' studios, the Cluny pub is now one of Newcastle's best small music venues, there's a city farm, a riding school, music rehersal studios and the National Centre for Children's Books is nearby. The building on the right in the picture above is the posh Hotel du Vin (rooms start at £160 per night), formerly the Tyne Tees Steam Shipping Company headquarters.The derelict building with the chimney is an old Maynard's toffee works, now scheduled for redevelopment as a business centre for high-tech design studios. Nature, of course, has been creeping back here ever since the old industries closed. 

The latest development is a lock at the junction with the Tyne, which has converted the Ouseburn from a linear muddy puddle at low tide into a permanently filled canal ... with a small marina for pleasure boats (mostly converted ship's lifeboats). Just around the bend in the river in the picture above are all the new developments mentioned above.

There are some surprising wild flowers here. This is ramping fumitory, a sparsely distributed species in Northumberland that's usually associated with hedgebanks around arable fields in rural areas.

How come it's here, in the heart of the city? It probably arrived in hay for horses and has clung on - literally, it grows in cracks in walls - ever since.

Brambles (some ripening already) would have been early arrivals, in bird droppings. This is probably one of the best sites for brambling in the Toon, within a  mile of Newcastle city centre.

When nature comes back, people want to come back too. What I find fascinating about the Ouseburn is that, whenever I visit, nature has reconquered a little bit more of what was once an industrial hell-hole.... often with some inspired help from imaginative people. When the lock was built it created a canal with bare concrete walls, so to introduce wild flowers along the water's edge floating islands like this one were constructed, filled with waterside wild flowers and anchored to the wall.

Here's another one, under a mass of flowering brambles dangling over the wall. Purple loosestrife and winter mint are currently blooming in profusion on these islands......

... and the purple loosestrift was at its best this morning. Without these man-made islands there would be nowhere for it to take root.

At a time when almost all wildlife news in the media seems to be bad news, it's uplifting to visit a place like this where a century and a half of destruction is being rapidly reversed. This shoal of fish, cruising the surface waters of the revived Ouseburn this morning, seemed to be enjoying the revival and thriving .........  anybody know what species they are?(double-click for a larger image)