Tag Archives: Gunnersbury Triangle Nature Reserve

A Surprising Workday with London Wildlife Trust

16 October 2014 Ian Alexander

Most of my last few visits to Gunnersbury Triangle have been taken up with untangling a mass of fallen Willow trees in the mangrove swamp. One tree fell on the next, which fell on the next … and the whole lot were in sticky mud with a rising autumn water table, covered in ivy to boot. I lopped, chopped and carried branches and lumps of ivy away, getting happily hot, tired and dirty in the process.

Yesterday I wandered around with no tools other than camera and binoculars, and was rewarded with the sight of a Grey Wagtail, a Robin and a Wren hopping about and feeding in their different styles, exactly where I had been clearing.

The wagtail was gobbling mouthfuls of grubs that it grabbed from the soft mud. It constantly bobbed and wagged its tail, displaying its yellow rump in the process. Could that be aposematic – is the yellow, in other words, a warning that the bird is distasteful? If not, why does it constantly flash yellow, even when no other birds of its species are about?

Today, I finished lopping the fallen Willow branches; as these last ones were over on the side, it was a cleaner and drier job. Then I joined in with a corporate group from Lend Lease, a well led and relaxed team … of property developers. They were incredibly pleasant to be with. The next surprise was at the hut when we all had a cup of tea: a nice Indian businessman in a suit came and asked us if his firm of engineers could use the reserve … for a group meditation. They stood about quietly and respectfully in a group, at least one person with hands pressed together in the ‘namaste’ position. We went on clearing and coppicing in the delightful autumn weather.

I got a small winged bug in my mouth; it released a pungent taste of cinnamon oils. Probably that is a chemical defence too: certainly a powerful taste, probably unpleasant in any quantity; but it was not bad in a one-off dose.

I ended my day sawing off some of the tree-stumps left over from the coppicing, together with one of the very capable and enthusiastic London Wildlife Trust trainees. It’s tremendous to see such good work going on in the reserve. And a piece of excellent news: a new warden has been appointed to manage work on the reserve, along with a West London warden who will be based here, but will have the massive task of keeping all the Hillingdon reserves from getting totally overgrown with hawthorn and blackthorn, among other things. So, suddenly, the place is full of life! Let’s hope we soon get our new visitor centre, we need it.

Conservation work with property developers; meditating engineers. You couldn’t make this up, or if you did, nobody would believe you. People say nature opens your mind, helps you feel relaxed. It does, you know.

Conservation, Nature Reserves

Opening up the Mangrove Swamp

9 October 2014 Ian Alexander

Today, down at the nature reserve, it was a day for work and weather rather than natural history. A vigorous Low was working its way across the top of Britain, with a brisk, freshening southwesterly wind bringing little showers across town. The water table had risen appreciably in two days, and I was glad of my gumboots, as I had decided it was time to do something about the overgrown ‘Mangrove Swamp’ in the middle of the reserve.

I should explain at once that we don’t have any coral reefs or fringing banks of Rhizophora mangroves here in Chiswick: that would be a fine thing. What we do have is a wet hollow – probably once a tributary of the long-gone Bollo Brook, one of London’s lost rivers – with attractive carr vegetation. Carr means wet woodland: we have willow of various species (probably mainly crack willow), birch and an assortment of other trees in the drier places – sycamore, hazel, holly, rowan, cherry, oak. But down in the Mangrove Swamp the willows predominate, their feet in the water for half the year. They grow rapidly, and then fall over; or branches get shaded out and die. The result, quite soon, is a tangle of lodged trunks and dead wood that cuts off the view and fills up the hollow, part of the natural succession, but tending to make the reserve less diverse (I think) and less interesting to look at. (I’m reflecting on whether one should be “managing” a “nature reserve” at all, given what George Monbiot says in Feral – he’s all for leaving nature to itself – but in a small reserve in town, management does seem necessary. Perhaps it’s a nature garden or something, not really a reserve at all.)

I cleared a mass of broken or cut dead wood from the wet floor, putting it to one side – it will still be available for fungi and beetles to consume. I then cut several long, heavy willow branches, mostly dead or dying, that had fallen most of the way to the ground across the mangrove swamp. A couple of hours hard work (I completely forgot about the brisk wind) had the main area cleared. We then set to and cleared what seemed to be a dark shrubbery near the boardwalk, but which was actually a large fallen tree shrouded in a six-foot thick mass of ivy. It was satisfying to get it clear; the tree trunk will need chainsawing, however.

After a well-deserved cup of tea, I pruned the hedge that was overhanging the street, pulling down a mass of strong twining hops that had scrambled all over the hawthorn. Blood-red haws rained down but there were plenty left when I had finished. Around the reserve, the rowans were in fine fruit, with some roses covered in scarlet hips.

Natural History, Nature Reserves

Golden Spindles

6 October 2014 Ian Alexander

I didn’t even bother to struggle round the Fungus Foray in the afternoon, as it was obvious from the dry weather of the last month that there wouldn’t be any mushrooms to speak of. So I wandered along to say hello to whoever came along, and perhaps see some other wildlife.

Sure enough I met Alick Henrici, the indefatigable mycologist; he leads fungal forays in every county, even the Grampian Fungus Group, so he gets about a bit away from his home patch in Surrey, especially Kew Gardens. He said there was nothing to see, barring a few certainties like Phoma hedericola (Hedera=Ivy) which forms small dried-out looking patches on “almost every Ivy leaf”.

Around the corner, as he had said, some children and their mothers were thoroughly enjoying pond-dipping. Most of the summer animals were nowhere to be seen – not a newt anywhere, hardly a waterflea – but I saw some Pond Skaters, a Water Boatman, a few tiny damselfly nymphs, a Hoglouse or two, and a couple of plump dragonfly nymphs.

Hoglouse, Dragonfly nymph, Ramshorn snail

A weird, soft screeching noise was coming from a small oak above the pond. It wasn’t quite the harsh screech of a jay, and if it was a crow it had a seriously odd high voice. I climbed up to have a look. A grey squirrel was the source. It was alone so it wasn’t clear why it was calling.

On the steps over the mound are some wooden posts to keep the uprights in place. And peeping through the wire netting on the mossy top of one of these posts was a teeny tiny clump of a yellow Ascomycete fungus, the ‘Golden Spindles’ toadstool, Clavulinopsis fusiformis. The holes in the netting are about a centimetre across.

Conservation, Nature Reserves, Wetlands

Tree-Felling, and a Drunken Picnic

14 September 2014 Ian Alexander

This week down at the Gunnersbury Triangle I found myself faced with a rather large challenge: a willow had fallen on to another willow, which … had fallen on to a third, which had fallen right across our little ‘Mangrove Swamp’ wetland at the end of the reserve, and was overhanging the boardwalk that we had all rebuilt last winter.

Fallen Willow across Gunnersbury Triangle's 'Mangrove Swamp' — Fallen Willow across Gunnersbury Triangle’s ‘Mangrove Swamp’

I cut off all the small branches for two other volunteers to drag away for dead-hedging. Then I sliced off all the larger wood I could reach. The rest was alarmingly high up, or far too large for a bandsaw: much of it will have to wait for a chainsaw team. We held a little conference, and I realized I could cut some more by scrambling up on a fallen trunk. I sliced through a largish branch, and the cut end gradually sprang back to the vertical, ending four metres up, and posing a nice puzzle for anybody wondering how it might have been cut! We cut up and dragged away the considerable pile of bits, and I ended the day with a pleasantly clear ‘Mangrove Swamp’ area, bordered by a neat line of large horizontal willow trunks, defended by a thicket of holly which had become trapped and had regrown all around the fallen trees.

Mangrove Swamp, cleared of fallen trees — Mangrove Swamp, some hours later, cleared of fallen trees (well, mostly)

The other odd thing that happened was that the picnic meadow was utterly befouled by a filthy assortment of broken raw eggs, cotton wool pads, mashed potato from powder, pieces of raw onion and raw ginger, and nearly empty bottles of vinegar and vodka. It smelt terrible. The team picked the stuff up with gloves and a litter-picker, and we speculated how it had arrived there.

Our story is that a group of new students at the start of term held a night-time initiation ritual there en plein nature, each initiate being required to take a bite of onion, mouthful of mashed potato, shot of vodka, swig of vinegar, etc etc, and to pay a forfeit of being pelted with eggs if they flinched. Or maybe they were pelted willy-nilly, who knows. And then perhaps they tried to clean the worst of it out of their eyes with the cotton wool.

Whatever the truth of the matter, there is no doubt that city-dwellers make contact with nature in a myriad ways. Some go birdwatching; some microscopically study pond life; some walk or run or cycle in green and pleasant places; some hold drunken picnics. Perhaps we should value nature (and nature reserves) for its ability to support all these activities.

Conservation, Natural History, Nature Reserves

Flaming June

5 June 2014 Ian Alexander

After all the rainy weather (I even found a large toadstool – in June: The Blusher, Amanita rubescens), today was suddenly hot, at least it seemed so while digging brambles out of the ramp meadow, raking up the scythed Cow Parsley in the full sun, pitchforking it into a barrow and carting it off to a deadhedge. It was a satisfying conservation job, one of those where you can see what you have done, and it looks a lot better after than before. The area is supposed to be a meadow; we successfully suppressed the overgrowth of brambles two years ago, leading to a burst of rather nice Garlic Mustard and its attendant Orange Tip butterflies last year: and a second wave of Cow Parsley that must have seeded itself really well, because it suddenly covered the area this year. Now that it’s all cut, we may hope that grasses and smaller herbs may get going: some Ground Elder at least has begun the process.

In the pond and on the vegetation for a way around it, including atop the hump, Large Red Damselflies are soaking up the sunshine, and flying in cop, egglaying – the females dip the rear half of their very long abdomens in the water to reach an aquatic plant such as Myriophyllum on which they place the eggs.

The butterfly transect was again quiet, but graced by the first Cinnabar Moth of the year: there is a fair bit of Ragwort coming up, and this adult must be newly hatched out of a pupa, presumably at ground level or below as the plants are annual.

Sure enough, after I had finished the transect, the first Holly Blue butterfly of the year, beautifully fresh and new, skipped its bright quick flight just in front of the hut.

Natural History, Nature Reserves

Grasses at Gunnersbury Triangle

3 June 2014 Ian Alexander

With the light changing all the time in a showery airstream (and the Met. Office seemingly unable to get the forecast right for the last several days, wrong every time to my surprise), things looked hopeless for butterflies (just a Speckled Wood or two) and insects (a few leaf beetles, hoverflies and bees).

So we picked up a field guide and a couple of identification sheets, and went out to see what grasses we could find between three of us.

Ryegrass is a tough grass useful in lawns. Its neatly alternating spikelets make it easy to identify.

Cocksfoot is a taller grass with a head that somewhat resembles the shape of a bird’s foot with its chunky branching spikelets to left, centre and right .

Soft Brome is as its name suggests soft to the touch; its spikelets like most Bromes are compactly plump and rounded, they form a pattern of green and white stripes, and they have awns (little barley-like spines). It’s quite distinctive once you’ve seen it.

Barren Brome looks very different: perhaps its name comes from the way it appears to have nothing much in its seed-heads, which are thin, triangular and very spiky; the plant is altogether long and thin and dark purplish-brown.

Yorkshire Fog, a beautiful name for a lovely soft plant, is thick and tall with broad soft leaves and a remarkably thick, soft seedhead. It’s one of those plants you can recognise twenty yards off once you know it.

The reserve has some False Oat-grass which in theory we should be pulling out – it seem unlikely given the way it’s tightly integrated with the rest of the grasses and herbs, so it’s probably here to stay.

There seem to be several Fescue grasses in the thin strip of acid grassland along the line of the old railway – the clinker that the sleepers rested on consisted of chunky angular chips of hard acid rock from somewhere far from London. One is Sheep’s Fescue: there may be Red Fescue, and there is something that looks like one of the taller Fescues too.

The Meadowgrasses have a typical light open panicle for their seedhead, giving a rather delicate appearance with their slim stems. I carefully checked which kind this one was; it has a pointed ligule where the leaf joins the stem, and is gently rough with little hairs, so it’s the Rough Meadowgrass.

In the woods near the path there are tufts of a broad-leaved grass that tolerates shade: it’s the Wood Melick. Finally, there’s one conspicuous grasslike plant that enjoys the wetter places here: the Pendulous Sedge. It’s a bit invasive but so handsome that I always admire it.

Natural History, Nature Reserves

Bugs Day at Gunnersbury Triangle

31 May 2014 Ian Alexander

Saturday 31 May was Bugs Day at Gunnersbury Triangle. The team arrived early to set out home-made cakes, lemonade, a face-painting stall, tables for children to paint butterfly cut-outs, signs advertising the day, and a wall-sized display of the Tree of Life, or rather a Tree of Invertebrate Phylogeny.

Throughout the day a succession of families with small children came and had fun decorating the butterflies.

The Tree of Life occupied a whole wall of the tool shed.

For the first time, we carried out a worm survey, organised nationally by Riverford organic farms (there’s a free identification guide to print out) – bizarrely, there is no map of the distribution of our native earthworms, so perhaps in a year or two there will be one now. We found no ordinary Lumbricus terrestris (Lob worms), the big ones that burrow deep under lawns (, maybe we needed to dig deeper), but good numbers of Black-headed worms (Aporrectodea longa, dark head, brown body, long and thin), a few smallish Green worms (Allolobophora chlorotica), and a Grey worm (Aporrectodea caliginosa, grey with a pink head and a pale saddle). It was surprising how many individual worms there were in a spadeful of earth, and the number of species. Darwin showed how important the earthworm was, but they seem to have been quite thoroughly neglected ever since.

An entomologist from the Natural History Museum led a guided walk on the bugs to be found in the reserve.

We gingerly plucked banded land snails from some tall stinging nettles, finding a good range of colour varieties from clear yellow to heavily striped with dark brown and black.

Woodland bug hunt - slugs, centipedes — Woodland bug hunt – slugs, centipedes.

In the woodland, the entomologist boldly ventured outside his special area (Diptera) to familiarise visitors with the range of local slugs, centipedes, millipedes and woodlice: bugs in the very broad sense. We did have some true bugs too: shield bugs that give off a warning stink when held between finger and thumb. And in between, ‘bugs’ often means insects in general.

The sawflies and ichneumon flies are difficult for non-experts as there are hundreds of similar species and no popular books. However, the sawflies have thick cylindrical bodies, whereas the ichneumons, like the social wasps, have a very narrow ‘waist’. The Hogweed flowerheads (very large white umbels of dozens of small flowers) played host to plenty of good big sawflies with yellow legs and waspish black-and-yellow stripes.

Nice side/tail view of Cuckoo Bee on Hogweed

A keen amateur entomologist (who recalled visiting the Triangle before it became a reserve 31 years ago) found this Cuckoo Bee. It parasitises and resembles ordinary bumblebees such as Bombus hortorum, but it never makes a nest or raises young. Instead, the females enter a bumblebee nest that already has a good number of worker bees, displace their queen, and lay their own eggs. Their brood is then brought up by the host workers. It’s a nasty way of life. The adults have a rather distinctive ‘tail’ with less ‘fur’ than usual.

The Hogweed was also feeding plenty of Tree Bumblebees, a smallish species with a bright orange-brown furry thorax and a black abdomen tipped with white, so they are distinctive and easy to recognise. Only ten years ago or so they were unknown in England, but common just across the channel. They seem to have arrived all by themselves – bumblebee expert Dave Goulson (see Book Reviews) found them by chance in the New Forest – and now they are common here. Perhaps their northward spread is part of a global drift of species and habitats towards the poles as the climate warms.

Micro-moth Nemophora degeerella - longest antennae of any UK moth — Micro-moth Nemophora degeerella – longest antennae of any UK moth

The entomologist found this beautiful micro-moth, giving the lie to any idea that they are all small and brown. Nemophora has a bold yellow-orange stripe across its forewings, making it instantly recognisable, but even more impressive are its antennae, which are over 4 times as long as its body (fw: 10mm): the longest antennae of any British moth. Quite a surprise.

Natural History, Nature Reserves

More a Bug than a Butterfly Transect

29 May 2014 Ian Alexander

I had a go at the ‘regular’ butterfly transect down at the reserve. It was warm and humid but overcast and it didn’t look promising. A large willow covered in Gypsy Moth caterpillars had been loosened by all the rain, and had fallen across the path. I lopped off the crown branches and carted them down to a dead hedge to fill in a gap someone had been climbing through.

The sun peeped out and the cloud cover reduced to maybe 60%, making it warm and pleasant. A single Small White appeared over the ramp and made it onto the transect. I wandered around the reserve, but there was nothing until I found a solitary Speckled Wood in the large meadow.

However, there was plenty to notice all around. The building site looks a lot better now the ‘Costa Concordia’ white horizontal balcony cladding on ‘Chiswick Point’ (well, it’s in Acton Green and on Bollo Lane, but I guess Bollo Block didn’t quite have the same cachet) has been completed: it will be nice when the noise of cranes and drilling stops.

Handsome iridescent green male Oedemera nobilis on Catsear

Many ichneumon flies were out on the Hogweed, some mating; almost every Catsear flowerhead had one or two handsomely iridescent green Oedemera nobilis, the “thick-kneed flower beetle” – only the males have the swollen hind femurs, but both sexes have a gap between the slender wing-cases. The males were of noticeably varying sizes, presumably the large ones having the best chances of mating.

Tent of Comma? caterpillars on Stinging Nettle — Tent of Peacock butterfly caterpillars on Stinging Nettle

A fine bustling mass of hairy black early-instar caterpillars of the Peacock butterfly, wriggled on their silk tent atop a Stinging Nettle.

Laburnum leaf beetle larva doing an impressive amount of leaf damage

The Laburnum by the main path is being eaten full of holes, probably a good thing for a non-native shrub in the reserve, by spotted and striped larvae of the Laburnum Leaf Beetle. Never seen it before.

The wild rose in the car park hedge was host to a mating pair of Rose Sawfly, a serious pest for gardeners but an attractive insect with a bright yellow abdomen.

Large Red Damselflies in cop over a lot of healthy Starwort in the pond

As if all these treats weren’t enough, there were Large Red Damselflies mating and egg-laying on the pond, Common Blue Damselflies, lots of Hoverflies, Click Beetles (seemingly Athous haemorrhoidalis), large brown frog tadpoles and small black toadpoles, singing Blackcaps, a Song Thrush, a Jay, and plenty more. Maybe it’s not just Bugs Day on Saturday, but Bugs Week.

Conservation, Natural History, Nature Reserves

Swifts Screaming High Over the Cow Parsley at Gunnersbury Triangle

27 May 2014 Ian Alexander

On a grey rainy day, I put on my waterproofs and go down to the Gunnersbury Triangle reserve. A newly-fledged Green Woodpecker flies off. The cow parsley has taken over the whole of the meadow by the approach ramp; last year there really wasn’t very much of it, but now the tall white umbels are quickly turning to seed-heads across the whole area: they need to be pulled up quickly before they ripen. They are accompanied by quite a lot of cleavers (sticky-grass), nettles, hogweed, even hops twining their tall fibrous way over the other plants. And a few brambles are coming up again: we had a blitz a year or two ago, pulling out most of them, and the meadow is much improved, but that hasn’t saved the rather nice garlic mustard (good for orange tip butterflies) from the cow parsley invasion.

I loosen one bunch of roots after another with a fork, and pull up the cow parsley roots – much like carrots, they’re in the same family. When the soil is shaken off they are a pale brown, some straight and carroty, some branched into five smaller swollen roots. When I have a big armful, I carry them down to the dead-hedge.

Digging again, a nettle manages to sting me lightly through the leather-and-cloth gardening gloves. I hear a screaming sound and look up: eleven swifts are wheeling together high overhead, the most I’ve seen over this part of town this year, indeed for many a long while. Sixty or more sometimes gather over the lakes at the London Wetland Centre, pausing to feed before moving on up north on their spring migration.

I gather another armful of cow parsley. The meadow is starting to look a little better. I pull a six-foot stick out of the herbage; half-a-dozen diversely coloured white-lipped land snails, some plain yellow, some striped with black, fall out on to the path. The polymorphism has been argued over by ecologists: it might be camouflage adapted to different backgrounds, some lighter, some darker; or more interestingly, it might be a way of defeating predators like Song Thrushes which could be searching for snails of a particular pattern, so if a bird had learnt that snails were striped and had that ‘search image’, that bird might not spot plain snails, perhaps.

It comes on to rain. I help out in the hut, making preparations for Bug Day when we hope the reserve will be buzzing with excited children and their parents. They will be welcomed by a smiling ‘GunnersBee’, who is a black-and-yellow cutout on a huge blue card with yellow cutout flowers. Even in the drizzle, several species of real bumblebees are busy gathering pollen and nectar.

Conservation, Environment, Natural History, Nature Reserves

Gypsy Moth plague

16 May 2014 Ian Alexander

The Gypsy Moth, Lymantria dispar, is a notifiable pest listed by DEFRA, or at least it was when that document was published back in 1997. The insect was announced to be “a serious pest of trees and shrubs” and nurserymen and landholders were required to notify DEFRA or the PHSI HQ immediately.

Gypsy Moth caterpillar on birch trunk: blue warts at front, red warts at back. The black-and-white pattern may also be aposematic

It has arrived in the Gunnersbury Triangle with the hairy dark caterpillar larvae with blue and red warts on their backs all over some Birch trees. The infestation is rapidly defoliating them, and causing substantial damage to some Oaks too.

Lymantria means ‘destroyer’, quite a well-named genus. The caterpillars are aposematic, their hairs and bright coloration warning off predators; the hairs are irritant, containing diterpenes, complex organic ring compounds found in wood and plant resins for defence against microbes and fungi, and retained by the caterpillars for defence against predators.

It will be interesting to see how the trees cope. Oaks can generally recover even when thoroughly defoliated; the Birches may suffer more. People can hardly use pesticides in the nature reserve, even given the means to spray whole trees safely, but biological controls are imaginable. The caterpillars are parasitised by Ichneumon flies, which may well be keeping Gypsy Moths under some sort of control in Europe. There were no controls in place to halt the spread of Gypsy Moth in America, however, where the pest was accidentally introduced in 1869 from Europe by the amateur entomologist Étienne Léopold Trouvelot. He was hoping to cross-breed them with silkworms to improve their disease resistance; he is remembered instead for starting a disastrous continent-wide caterpillar plague which still continues. Attempts with other pest species to introduce their predators or parasites have often proved unsuccessful and sometimes disastrous in their turn.

ObsessedByNature

Tag Archives: Gunnersbury Triangle Nature Reserve

A Surprising Workday with London Wildlife Trust

Opening up the Mangrove Swamp

Golden Spindles

Tree-Felling, and a Drunken Picnic

Flaming June

Grasses at Gunnersbury Triangle

Bugs Day at Gunnersbury Triangle

More a Bug than a Butterfly Transect

Swifts Screaming High Over the Cow Parsley at Gunnersbury Triangle

Gypsy Moth plague

The English seem unemotional … except for their passion for nature