All posts by Ian Alexander

Spring in the Air! Volunteering and Prototyping at Gunnersbury Triangle

First Comma of the year!
First Comma of the year!

Well, it only takes one still, warm sunny day and suddenly it’s SPRING! Sure enough, the frogs had gone crazy down the mangrove swamp, there was a great heap of spawn in the shallow water, and some excited children (and mothers). A pair of Comma butterflies wheeled and scurried about the sky in a long, intense dogfight, their whirling wings making it clear these were rival males of an orange species, if nothing else!

Hairy-Footed Flower Bee (Anthophora plumipes) male
Hairy-Footed Flower Bee (Anthophora plumipes) male

Mike expertly identified the Hairy-Footed Flower Bees around the Alkanets: they came out to warm up in the sun in some numbers. They have never been recorded before here, though we have surely had plenty of them, unrecognized.

Frogspawn in Mangrove Swamp
Frogspawn in Mangrove Swamp
Spring! Broom in bloom
Spring! Broom in bloom

The brilliant yellow of the Broom, and the foamy white of the Blackthorn flowers, announced that spring had sprung in a Botanical way, too.

Blackthorn in Bloom
Blackthorn in Bloom
The completed Hedgehog House prototype
The completed Hedgehog House prototype

The team spent the afternoon designing and making a prototype Hedgehog house out of Correx sheets left over from the Vole Patrol. We worked out a way to make a house from just two sheets, 54 x 120 cm each: basically one big tube folded 4 times to give 4 sides and an overlap flap, and two half as wide, one for the entrance tube, one for the two ends (joined along the ceiling with flaps on each end of the floor). We fixed it together with just 5 cable ties ingeniously stitched through bradawl holes. A challenge was to get the last stitch in, as the box was then fully closed! The trick was to take out the entrance tube and put a hand inside: the cable tie had to be poked out through a hole that of course we could only see from the outside! The result looks enormous and luxurious, so being Londoners of course we made a lot of jokes about Hammersmith Hedgehog Penthouses and luxury granite kitchens, etc etc. Anyway, we hope the hedgehogs will like them.

Vole Patrol 9: Perivale Wood

Vole Patrol, Perivale Wood, dawn
Vole Patrol, Perivale Wood, dawn

The first cycle of trapping at Gunnersbury Triangle has been completed, and the action has moved on to Perivale Wood. This beautiful reserve is owned by the Selborne Society, the oldest nature conservation society in the world, founded in 1885 and thus a few years older than the RSPB.

Despite its name, Perivale Wood includes pasture (for horses), damp scrub, secondary wood on disturbed land, some hedges (we saw one newly “laid”, the trunks almost cut through and fastened at an angle with beautifully-woven withies), three ponds and two streams.

This, of course, enables London Wildlife Trust‘s Vole Patrol, by agreement with the Selborne Society, to search for small mammals in woodland, by water, and in meadow.

Walking in, we heard a Song Thrush, and much calling and drumming of Greater Spotted Woodpecker and Green Woodpecker. From the bare Oak trees of the photo above, I briefly heard an early burst of song from a Chiffchaff, my first of the year.

Lindsey scribing the data
Lindsey scribing the data

We met some new Vole Patrollers, including Lindsey, seen here acting as “scribe” for the all-important data, and Nicola, seen here weighing a Wood Mouse.

Nicola weighing a woodmouse
Nicola weighing a Wood Mouse

The team quickly sorted itself out, everyone sharing the necessary roles – fetching traps, opening them, weighing, measuring, sexing and coding the mice, recording the data, returning the mice to their exact locations, baiting the traps, and returning them to their locations. It’s not really complicated, but there is enough to do, and with over 30 traps in the different habitats around the reserve, each task has to be done many times.

Vole Patrol in Perivale Wood
Vole Patrol in Perivale Wood. In the distance, team members are fetching traps. In the centre, a trap is being opened inside the large bag,for the catch to be weighed and measured. In the foreground, a mammal is being coded before release. And behind the camera, a team member is recording events!

Wraysbury in the Mist, and Leafy Lichens

Willow Reflections in the Mist
Willow Reflections in the Mist

Well, after 7 Vole Patrol postings, and some very cold, wet and early mornings, I felt like enjoying a nature walk in the sunshine, away from Woodmice. But as I left town I found myself in fog, not too thick to be sure, but fog nonetheless.

I was rewarded, however, with the lovely sight of the willows along the lake seeming to float, isolated in the smooth sea of soft gray.

As the mist slowly lifted, a pair of Goosanders and a pair of Goldeneye (the male displaying, the female in tow a yard behind) could be seen through the mirk.

I couldn’t get away from the mammals, either. I was pleased to see not just the usual Muntjac prints along the path, but Roe Deer too.  A little way further, and there was a Wood Mouse hopping in a relaxed way across the path, before diving down its hole.

Woodmouse hole
It went thattaway: Wood Mouse hole

Among the birds calling were Green Woodpecker (finely), Great Tit, Song Thrush, Cetti’s Warbler. A Heron and a Parakeet flew overhead. Wood Pigeons and Carrion Crows watched warily.

The damp air had another good effect: the lichens looked wonderful, and even the bristly Ramalina were soft.

Parmelia caperata
Parmelia caperata
Ramalina colony
Ramalina colony, generally hard, and the same both sides
Evernia prunastri colony, always soft, and white below
Evernia prunastri colony, always soft, and different below

It was nice to see the lichens flourishing so close to London (and Heathrow): these little fungus/alga plants are very sensitive to pollution, and when I was a boy they were almost impossible to find anywhere near a city, so conservation stories can be happy.

Vole Patrol 8: Capture-Recapture

My wife looked at me with a mixture of surprise and concern as I made for the door without breakfast. At least have a coffee, she said. I poured a cup of the hot steaming milk and espresso, and drank it alla Milanese, standing up, rapidly, with a minuscule bite to eat, before rushing off to work. Though in my case it was not so much with immaculate suit and the slenderest of briefcases, as with gumboots and mountain waterproofs from top to toe.

The traps had been out overnight, not so cold now but definitely wet. I went off to pick up a row of traps: all six had been triggered, and they felt heavy, as if mammals were within.

Back at the analysis point, Huma and Ollie had set up a Base Camp that Bear Grylls would have been proud of — a neat tarpaulin arrayed with all the equipment, underneath a canopy stretched on baletwine between four trees. The rain dripped gently down, and the area around the tarpaulin turned steadily into mud.

We opened the traps one by one, gently picked up the Woodmice, identified them by the code marks clipped into their back fur, and weighed them. Identification is not as easy as it might sound, as mice wriggle, and the marks are not necessarily exactly where they ought to be. We’re also reusing the same codes for males and females, so we have to sex the mice. At least the males are generally larger, wrigglier and heavier, so a guess is likely to be right, but weights overlap and the external signs are not very different, mainly just a larger distance between the two openings in the males, unless the testes are big enough to give telltale bulges at the base of the tail.

Out of 20 mice caught, same as yesterday, 19 were recaptures, giving a population estimate in the trapping areas of about 21 mice by the Lincoln-Petersen capture-recapture method.

Of course there are plenty of reasons why the estimate might be wrong, not least that the animals which have been caught learn that the traps are warm, dry, safe, and full of nutritious food. They may, in short, have become trap-happy, getting themselves recaptured as soon as possible!

All the same, the high rate of recapture does suggest that the population is fairly static in the area, and not terribly large.

We have only caught Woodmice in the traps here. It remains possible there are Field Voles in the meadows, but we have few meadow traps, and only near the edges: and if there were voles here, their population would be low after the winter, so we’d not expect to catch many.

Vole Patrol 7: Massive Morning Catch!

Vole Patrol coding measuring recording
Vole Patrol  hard at work! Coding (clipping fur patches), measuring, recording

I’m so cold! My feet are frozen! said Huma. It was indeed a chilly bright winter’s morning. We were grateful when the sun came up and warmed the glade where Vole Patrol had set up its measuring station, with tarpaulin, big sacks for opening traps, small bags for weighing and measuring, all the traps in order, scissors to code the animals’ backs, rulers, scales, fresh hay and three types of bait.

Mouse from M3 - hold still now
Mouse from M3 – hold still now

Unlike the meagre daytime catch of yesterday afternoon, 20 of the traps contained mice.

I had a go at measuring and coding; then Huma put a mouse back in the big sack, as if just out of an opened trap, and under her watchful eye I caught it gently by its scruff, transferred it to a small bag, and weighed it. I’m a mammal wrangler! The main difficulty, apart from their remarkable ability to escape, is that they hunch up, making straight-line measurements rather tricky.

Mouse from M2
Mouse from M2 – a female

Only one other trap had been triggered, so the false alarm rate was well down now: resetting the sensitivity of all the traps had been more than justified.

Wood Mice have big round ears
Wood Mice have big round ears

We were soon very busy: bringing in the full traps; opening them, catching the mice, coding their back fur, measuring, weighing, carrying them back to where they came from and releasing them.

Measuring and recording the weight
Measuring and recording the weight

Tony the ecologist, who helped with the trapping today, said he’d expected Wood Mice rather than voles. Voles cannot easily make their way along railway embankments as they’re predated by Foxes and Badgers, which freely use railway  “corridors”. Small isolated populations can easily die out, which is probably what happened here.

Vole Patrol 6: First Catch

Woodmouse in hand
Wood Mouse in hand

We approached the now armed and possibly triggered traps with some excitement. Of the six traps in “our” row C, four had been triggered. We picked them up, locked the other two so we wouldn’t catch any more mice while we were analysing the catch, and brought the four traps to Huma.

She opened trap C6 inside a large bag. A Wood Mouse shot out into the bag. I got a very blurry picture of a shadow behind the plastic.

Opening the first trap C6
Opening the first trap C6

Huma reached for the Wood Mouse. It bounced speedily up her arm, through the gap at the top of the bag, and hopped away over the tarpaulin. None of our other traps had anything in them. I must have looked disappointed as Huma told me there would be more.

Luckily there was: one of the meadow traps had caught a fine large male Wood Mouse.

It's a Boy
It’s a Boy
Wood Mouse has a yellow patch on chest
Wood Mouse has a yellow patch on chest

We sexed, coded (A = clipped patch on left shoulder), measured body length and hind foot, and weighed the mouse. It wriggled quite hard and almost escaped, but Huma was quicker.

Mouse A's fur is clipped on left shoulder
Mouse A’s fur is clipped on left shoulder
Measuring the hind foot
Measuring the hind foot
Weighing
Weighing

Then we took the mouse, still in its bag, back where it came from and let it go. Likely it will feast on the plentiful bait in the warm dry trap again.

Out of 32 traps, 8 had triggered and 2 had mice in them, much too high a false alarm rate, so Huma reset their sensitivity for tomorrow morning.

Vole Patrol 5: Woodmouse Woz Ere

See Vole Patrol 4: Baiting not Trapping

I stumbled out of bed a bit late this morning and only just arrived in time to join the Vole Patrol team. The good news was some sunshine, birdsong (Song Thrush the highlight, with Great Tit, Robin, Dunnock, Long-Tailed Tit) for the dawn chorus, and proof from many of the traps of mammal activity.

Woodmouse Woz Ere
Woodmouse Woz Ere

Without wishing to get too scatological, a Wood Mouse laid some definitive, er, evidence of its presence on the door of this trap, which does bear an uncanny resemblance to a miniature toilet. There are actually 2 mouse droppings (the other one is on the hinge) in the photo.

It’s  a mouse dropping, not a shrew’s, as shrew poo contains so many shiny, slippery insect cuticle fragments that it tends to fall apart, whereas these pellets have the solid consistency of a mouse’s diet of seeds.

Huma mixing bait (photo Joanne from Grow Chiswick)
Huma mixing bait (photo Joanne from Grow Chiswick)

Other traps had had their bait balls eaten (but not the maggot larvae, which shrews would prefer); some had bait crumbs outside their entrances, and others had leaves dragged inside, as if to make a nice warm nest.

Ian labelling traps (Joanne photo)
Ian labelling traps (Joanne photo)

Jo took these fine photos a day or two ago. I seem to have enjoyed labelling those traps!

 

 

Vole Patrol 4: Baiting not Trapping

See: Vole Patrol 3: Baiting Traps

At quarter to seven this morning we wrapped up well against the cold, on a beautiful clear day, the crescent moon glowing in the southeastern sky, and gathered at the hut. After a welcome cup of tea, we picked up haversacks full of boxes of bait balls, a little bag of apple slices and another of maggots, and a rubbish sack. We trooped off down the reserve to inspect the traps arrayed around the wood, meadow, and pond.

Was there a mammal in here? Inspecting one of the Waterside traps
Was there a mammal in here? Inspecting one of the Waterside traps

A Song Thrush sang loudly and beautifully from the Willow Carr thicket.

Bait Taken from Meadow Trap
Bait Taken from Meadow Trap

In the anthill meadow, trap M3 showed unmistakable signs of a mammal visit spilling from the entrance.

Did we catch something by mistake?
Did we catch something by mistake?

Another of the meadow traps caused a flurry of excitement. The trapdoor was up! Had we somehow caught a mammal, despite checking that all the trapdoors were locked down? Huma carefully opened the trap in a large plastic bag to prevent escape. There was nothing inside. Probably the trap had been left with the door closed.

Making Bait Balls
Making Bait Balls

Back in the hut, still with surgical gloves on, we mixed up more bait and rolled it into balls. The little boxes that protect the bait balls in the haversacks are on the table.

 

 

Vole Patrol 3: Baiting Traps

See Vole Patrol 2: Shrew Poo

Trapdoor locked open for baiting
Trapdoor locked open for baiting

Today we began a week of intensive trapping. Huma wants to survey the small mammals now, before there is any risk of catching pregnant or nursing mothers. So we are going to put out and check traps every morning and evening.

The traps we’ll be using are a new design of tube trap. They are less fiddly than the old aluminium Longworth traps, and a lot cheaper too. Huma thinks they’re “volunteer proof”: we wonder. Being plastic, they are warm and comfortable for the mice, voles and shrews we hope to catch.

Huma instructing the trapping group
Huma instructing the trapping group

We learnt what to measure, and the distinguishing features of the species that we may see. Huma explained how we would set out the traps, in a grid of three rows of six traps (so, A1 .. A6, B1 .. B6, C1 .. C6), evenly spaced in the woods, with four more up in the trees (T1.. T4), five in the meadow (M1 .. M5), and five near water (W1 .. W5).

Labelling tube traps
Labelling tube traps

Each trap has two parts, so I painted its name onto each half.

We grouped the labelled traps into neat carrying trays.

Hay, Apple, Bait Balls
Hay, Apple, Bait Balls

While I was painting, the others rolled chicken feed, peanut butter, seeds and water into bait balls.

Checking the Tube Traps
Checking the Tube Traps
A sprinkling of frozen maggots
A sprinkling of frozen maggots

Then we put a handful of clean hay, a bit of apple, a bait ball, and a sprinkling of frozen maggots into the round end of each trap, armed the trap, locked the door open, and clicked the two halves together. The first two days and nights we don’t want to catch anything, but to accustom the mammals to visiting the traps.

We lined up in the wood, carefully set down the traps along natural edges, and marked their positions with hazard tape.

We have to visit them at 7am tomorrow morning…

Book Review: Islamic Geometric Design by Eric Broug

Islamic Geometric Design by Eric Broug
Islamic Geometric Design by Eric Broug (with Moroccan Zellige tilework)

Eric Broug’s Islamic Geometric Design (Thames and Hudson, 2013) is as big and beautiful as Luca Mozzati’s Islamic Art. Like that book, it goes some way towards correcting the bias – the total blind spot to be frank – in Lynn Gamwell’s otherwise splendid Mathematics + Art on all things Islamic.

Broug’s focus is sharply on how to create such designs: both, how the Islamic craftsmen who made them did their job centuries ago, and how you can do it today. The book ends, indeed, with an Appendix of some 50 pages on “How to create designs”. The body of the book looks at Basic Design Principles, Grids and Polygons, and then 4-fold, 6-fold, 5-fold, and Combined Geometric Design. The focus is thus on geometry pure and simple, referring from there briefly to the history of each object covered.

Unfortunately, although the cover shows a fine example of Moroccan “zellige” tilework, the book is almost entirely devoted to the more rule-based geometric strapwork called girih, which one may guess was more interesting to someone like Broug, who plainly likes a tough geometric puzzle to solve. Girih can, it seems, be constructed either as was traditionally supposed simply with a ruler and compasses, or, intriguingly, with a small set of “tiles” (conceptual rather than ceramic), which can be assembled and arranged in an almost infinite variety of ways, including aperiodically (a fascinating aspect if you’re a mathematical physicist).

Many of the objects analysed in the book are walls, ceilings or domes of buildings, such as mosques, medersas and mausoleums. Happily, however, many other examples are taken from woodwork including minbars (pulpits), bronze doors, tiles and screens, with the occasional plate. Broug is mainly interested in the very strictly geometric Girih strapwork designs, which can be analysed rather thoroughly with geometry; he is less interested in the far less mathematical Zellige of Morocco, arabesques, or calligraphy, which are all important forms of Islamic decoration; and he does not concern himself with the making of artefacts such as glass, ceramics, paintings, or metal objects except insofar as they are geometrically patterned.