Drought and the plough: the subsidence ponds' tough summer

July has been an unlovely mix of cloudy, clammy days. Nonetheless we have had little sustained rain and the effects are obvious as the Bay’s smaller wetlands dry out.  Not a problem in itself, especially with the mosaic of pond types scattered across the landscape.  Perhaps a greater threat is the interplay between the weather and other forces, in particular land management. For example this subsidence pond at the south of the Bay at Ellington Farm. These fields are dotted with seasonal ponds, shallow bowls that fill every year, roundels in winter then choked with the ephemeral mayweeds and oraches of disturbed ground in summer. You can see the white splodges of scentless mayweed in bloom. This pond has been the summer hangout of avocets and gulls in recent summers but not this year. The dry weather has allowed the wheat to grow thick and strong a long way into what is normally the pond’s core. It is now a small remnant, forlorn in amongst the crop. The dry ground also means that tractors can plough through, rather than round.

It could be worse, for example this pond.

 

It’s not there. You can make out the faint curve where it has been but this summer a solid mass of wheat.  There are none of the characteristic plants in amongst the phalanx of stalks, only a huddle of pineapple mayweed along the distant hedge line edge.

Pond and their wildlife can cope with drying out, so long as there are refuges to retreat to then re-advance from. However the dry weather has tilted the balance in favour of the intensive cropping.  The land use looks to be the greater threat to the pondscape’s survival rather than the dry summer itself.  It is a classic threat, a double whammy of drying out and land use intensification. Wildlife can ride out the occasional mishap. But multiple stresses take a toll.  The subsidence ponds are having a tough year.

 

The drought canyons of Cresswell

 

The summer drying has come to Druridge Bay. In recent years I have done a regular walk every two to three months around the ponds at Blakemoor Farm. Many are temporary, whether in the dunes, grassy pasture or in amongst the arable crops. Most of them dry out in most summers, but not all. This summer though the drying out has claimed some new ponds.

 

The one in the photo is tucked away out of sight in pasture along the dune road and has never dried out since I started the walks in 2010. A spring seems out on the western slope and maybe this has kept it topped up whilst those around recede and dry. This summer though the whole pond has dried away, leaving a crazy-paving styled substrate of cracked mud. The cracks are six or more inches deep, zig-zagging between columns of concreted mud on which tiny plants perch, small tufts of pineapple mayweed or cudweed.  Down in the dark, cooler chasms the mud is not wholly dry, but these rifts create a oddly out of scale world. Individual columns of dried mud can be lifted out and replaced in a 3D jigsaw. This pond has always teemed with tiny invertebrates such as ostracods and chironomid midge larvae, a refuge in previous dry summers. The gloppy mud stayed largely free of aquatic plants, the water from the spring suspiciously high in conductivity, a hint of mine water perhaps from the abandoned seams of Ellington Colliery below. Why it should dry so completely this year I do not know but it is sad to see, a dry pond seldom worries me; temporary ponds benefit from a dry phase, however this seems strange. The gulls and teal of summer that once loafed around its rim, dawdling through July and August are gone and the field does not seem quite right.



Northumberland's shores and the geranium sea

Druridge Bay is decked out in its high summer finery. The dunes in particular are an intense barrage of colour: the yellows of ragwort, bird’s foot trefoil and ladies' bedstraw in amongst a pink-purple haze of bloody cranesbill. The cranesbill is so abundant that it is easy to take for granted, covering very dune face and hollow, even scuffed tufts hanging over dune paths. Try strolling out from Druridge Country park onto the dune-scape just beyond and the landward side of the tall dunes is a vivid sward of pink. They are wild geraniums, Geranium sanguinium. The odd sounding common name is not a botanist’s irate curse but a reference to their seed ponds that resemble miniature beaks of herons and storks and which become increasingly blood red in hue as summer advances, as if dipped in gore. You can make out a few of the pods, pointing skyward but still largely green in the photo above. So abundant is the bloody cranesbill along the Northumberland coast that it would make a good icon of our summer coast. From Berwick upon Tweed down to Tynemouth this geranium is widespread. Elsewhere around the shores of the UK it is scarce. I don’t know why this should be. It seems a tough and successful plant, surviving our north sea ravaged winters and summer sea fret. Right now just take time to gaze out over the pink haze to the blue north sea, ideally with a colourful cobble bobbing in picturesque cliché just off shore. The North Sea sounds too cold a name for July. Even if only for a month the dunes bright hues make these northern shores a geranium sea.

 

The southern hawker dragonflies and the hailstones

Southern Hawker dragonflies, Aeschna cyanea, have been emerging for the last week. I’ve only found a few of the old cast skins, called exuviae, so far, spooky and forlorn still clinging to sedge and reed stems as if they may be reanimated and crawl back into their ponds, but I’d not spotted any adults. Until today. Our region was hit by ferocious thunder storms last night, with hail stones the size of musket balls ricocheting around our back yard. This morning two newly hatched hawkers, maybe a bit subdued by the ominous weather and still not fully coloured up, were clinging to the cover of iris and reed stems at a nearby pond.  They will soon acquire the vivid bright green or pale blue bands that make them a very colourful insect.  As they whizz past I’ve heard startled passers by mistake them for very large wasps. The two conspicuous patches on the top of the thorax are particularly useful for identification. Once hatched and coloured up they will be away, often hawking along paths and woodland edges and taking their time before heading back to the wetlands of their birth. If you can get over the panic of “a very large wasp” take your time with them; the southern hawker is well known for its habit of inspecting you with as much interest as you might take in it. They will repeatedly fly up to you, check you out and seem as intrigued by your presence as you might be by their beauty. “Southern” is a bit of a misnomer. They are now quite at home this far north as this map from the nbn gateway shows : the yellow squares are 10x10 km grids from which the species has been recorded source, https://data.nbn.org.uk/Taxa/NBNSYS0000005626)

A blue tailed damselfly wash and brush up

Blue tailed damselflies (Ischnura elegans) have joined in the summer fun. It may be my imagination but they seem the shyest of the local damselflies, diminutive compared to their cousins.  Common red damselflies have an assertive flight, positively bossy in manner . They are on the wing early too and have been quartering their wetland homes for a few weeks now. Azure damselflies are also purposeful, zippy, an effect accentuated by the vivid almost all over blue of the males. The blue tails though tend to be more wary, fluttering into cover if you approach too boldly. The males are a slate grey with the blue spot at the end of their abdomen sometimes seeming to be in flying solo if the rest of the damselfly is obscured amongst the sedges and herbs. The females are even less conspicuous, although if you can sneak up close you’ll often find one flushed with a lilac thorax (the middle part of the body, bearing the wings and legs) or pale chestnut. This little male is giving himself a wipe behind his eyes before setting off on patrol, stretching his left foreleg over his head to wipe any specks from his bulbous eyes.  His blue tail spot is not fully coloured yet, but will become more intense with time. Watch out for blue specks floating through the plants around wetlands; each speck is likely to be a male blue tail, even if the rest of him is hard to see.

Sun, sex and suspicious parents: damselflies get the same hassle

 

Summer’s damselfies are lifting off in glittering droves. The azure damselflies (Coenagrion puella) have coloured up and the air can seem full of bright blue cocktail sticks deftly exploring the grass and rush swards, or perched up sunning themselves. Times are good in the heat. The males particularly are fidgety, landing for a few seconds then flitting up to argue. They seem unable to leave each other alone. Females tend to be cannier keeping out the way, only venturing out into public when ready to mate and provoking a rash of males to chase after them. These two are mating, the male the bluer one, the female a delicate green, hiding away  a bit in the reeds because other males will attempt to barge in, crash landing to knock them apart. Females will mate with several males. This makes life fraught for all concerned. Males endlessly pester. If a male mates with one female then unwisely abandons her another male can come in, mate and physically remove the first males sperm (I am sure you can find out how but be careful what you web search for). As a result it is much more usual for pairs to stay together for a while, the males going in for what is called mate guarding. The female uncurls from this mating wheel whilst the male maintains his hold around the back of her head with special claspers. They can fly off in this tandem, surprisingly fast. The male keeps a firm hold when they land, his legs folded, sticking up over the females head like an ornate hat whilst the female dips her abdomen into the water to lay her eggs. They still get hassled by single males, but at least they don’t have their parents turning up, unlike in the TV series

Schrödinger’s cat, the Large Hadron Collider and Cresswell's mysterious tadpoles

 

 

 

Blakemoor Farm’s new field corner ponds are doing nicely. The freshly hatched tadpoles of a couple of weeks ago (see 3rd April) are now plump and assertive. They are also playing statistical games. In one of the ponds all the tadpoles are squirming together in a dense black swarm. In the next door pond they litter the sediment, scattered with a pleasing eye for complete coverage. In a third pond there are none.  Statistics are not what inspires many people’s interest in  natural history, although I know of mathematicians who have been lured into ecology on the grounds that it is much more challenging. Statistics have their uses though, especially to summarise and test observations. The trouble is when nature plays fast and loose like these tadpoles. In the first pond there are fairly simple quantitative methods that will tell you that tadpoles have a clumped distribution, whilst in the second pond that they are more or less evenly scattered about. The trouble is that the perfectly clear maths makes no sense overall because the tadpoles are doing different things in different ponds, or not turning up at all in the third pond. I doubt that the Large Hadron Collider, turned back on again today to crack even more secrets of fundamental particles, could help unravel the problem of the mathematically inconsistent tadpoles.  Tadpole uncertainty may not have the ring of quantum uncertainty or the fame of Schrödinger’s cat as a conundrum but they are a lovely mystery right on our doors step, just over a wall from the dune road.