Friday, 26 July 2013

Gatwick's Alien Invaders

A battle is being fought all around Gatwick Airport... Aliens landed here quite some time ago, but together JS Agriculture and Gatwick Greenspace Partnership have plans for defeating these invasive species!

American Signal Crayfish (Pacifastacus leniusculus)

Signal Crayfish burrows in the bank and Himalayan Balsam growing along
 a section of the River Mole at Povey Cross

An important part of our Biodiversity Action Plan is to monitor the presence of non-native species occurring on Gatwick's land and to come up with plans to tackle them. As they have been established in our countryside for quite some time they are virtually impossible to eliminate, so instead we aim to control them as best as possible, reducing their impact on our native flora and fauna.

Bucket 'o' crays:  They have reached plague proportions in our part of the River Mole.
We humanely euthanise them under instruction from the Environment Agency

Tiny wee Signal Crayfish from the River Mole

The American Signal Crayfish (Pacifastacus leniusculuswas introduced to Britain in the 1970's and escaped from fish farms into our waterways. Having witnessed the size and quantity of their tiny larvae I'm not surprised they did! They are tough little pioneers and easily colonised our waterways; unfortunately they carry a disease which our native White-Clawed Crayfish (Austropotamobius pallipes) is vulnerable to. As a result White-Clawed Crayfish are now pretty rare and highly protected in areas where they still remain.

Our licensed crayfish traps with fish bait. 

Signal Crayfish have a voracious appetite and eat whatever they can get their claws on, be it aquatic plants, fish fry or invertebrates. They also burrow deep into river banks which causes destabilisation, erosion and eventually bank collapse. By trapping them on a section of the river and reducing the number of large, voracious adults I hope to see a positive effect on the aquatic biodiversity.

Gatwick Greenspace volunteers Adrian and James removing Himalayan Balsam; 
waders are not such a bad job on a hot summers day

Another problem alien here is Himalayan Balsam, which was introduced to Britain in 1839 as an attractive ornamental garden plant. It is a rapid coloniser, spreading along our waterways, growing very tall and quickly out competing our native flora. It has impressive pink flowers which are a good nectar source for bees and other pollinators, but perhaps at some cost to our own native wildflowers.

Himalayan balsam (Impatiens glandulifera) in flower

The root of the problem: the fleshy roots die back each winter, meaning the soil is left loose and exposed. This however does mean it is easy to pull up. 

The seed pods are pressurized, popping open at the lightest touch, scattering seeds into waterways which are then carried far and wide. The roots of this plant are weak and die back each winter, resulting in exposed mud which then erodes easily away .

Gatwick Greenspace volunteers are all-weather people with the correct gear, precautions and an ample supply of refreshments (I can testify to their high-standard biscuit selection!) On one of the hottest days of the year, they tackled a good length of the River Mole around Povey Cross, pulling up every individual balsam plant they could find.

Balsam is heaped into piles to rot down before it has flowered and seeded

Volunteer Georgina with a near full-grown Signal Crayfish

Gatwick Greenspace Partnership conservation volunteers at Povey Cross, North West Zone

The JS Agriculture team, balsam-bashing in the southern part of Horleyland Wood,
 Land East of the Railway Line

We are continuing the fight against Gatwick's invaders for the next few weeks. If you interested in volunteering and conservation around Gatwick then check out the website for Gatwick Greenspace Partnership, part of the Sussex Wildlife Trust.

Thursday, 18 July 2013


People may question how I spend my Friday nights, but this is a perfectly healthy pursuit and I think you all just need to open your minds.

Genuine question moth-trappers get from passers-by... 'Is that for aliens?'

Ok, so maybe moths are not everyone's cup of tea, but you could change your mind after meeting Jacob Everitt; local countryside warden and fellow moth-appreciator. Last Friday Jake brought his large moth trap to Gatwick along with mercury vapour bulb, generator, collecting pots and bags of knowledge and enthusiasm. We picked our site carefully, setting up in the North West Zone on the path between the River Mole and Brockley Wood.

 All moths are encouraged to drink responsibly

Face-moth surveying (best to keep your mouth shut)

Common Toad which was passing by, possibly also wondering what was going on

It was a pretty successful night for trapping; warm with virtually no breeze. Many different moth species were drawn in from the bordering scrub, woodland and wetland habitats, along with every biting midge and mosquito within a 2 mile radius. No one actually knows for sure why the moths are attracted to the light; the theories range from them being attracted to the warmth, them believing it is the moon (which they might navigate by), or simply to make adult people scream in bathrooms. 

Trappings of success - Moths can be put in the fridge overnight to settle them down. I prefer taking amateur pics of wildlife in-situ but the light of day does these guys most justice.

Close-up of a Peppered moth - all were re-released close by to where they were collected

The next day was quite a job of photographing around 30 different moths! Some of the other species we saw were scarce or under-recorded, so of great interest to recorders like Jake. They can give clues about how our management is affecting their diversity and whether they are in good numbers; after all they are pollinators and an important food source for other wildlife. I have a put together a folder with all my shots and the species names here (NWZ Moth Trap) but you can see below for a selection of the best of Gatwick's moths!

Peppered moth



Elephant Hawk-moth

Common Emerald

Peach Blossom

Angle Shades

Riband Wave (ab. remutata)

Buff Arches



And finally, an adult male Glow-worm (Lampyris noctiluca). These guys were mistaking the green light on Jake's generator for a glowing female. We recorded a total of 9 this way!

There will be more Gatwick moth-trapping to come later in the season...

Wednesday, 10 July 2013

Roving Records - North West Zone: 05/07/13

As much as I enjoy the outdoors part of my job, balance is firmly kept in The Force by hayfever. Why, why must hayfever be a thing?

False Oat-Grass (Arrhenatherum elatius) in flower

Last Friday's reptile survey resulted in just 3 small Grass Snakes, probably because I left it a bit too late in the morning and they had already charged up for the day. It was a great time for macro-invertebrate recording though as it was hot-dang (not complaining!) We are trying to build a picture of all species groups which occur here as part of our Biodiversity Action Plan; invertebrates are an incredibly important part of the ecosystem and can often be overlooked in conservation work.

Azure Blue Damselfly (Coenagrion puella)

An ex-Azure Blue Damselfly

The culprit: a pretty little Common Stretch-Spider (Tetragnatha spp.), here feeding on a fly

Due to the cool start to this season many species have taken a few weeks longer to get going. I began my trek at the Compost Field where the pond scrapes always come up with the goods: plenty of chaser dragonflies, darter dragonflies and damselflies were all getting on with things. Along the River Mole Grasslands were a good number of butterflies including Ringlet, Meadow Brown, Small Heath, Common Blue, Small Skipper, Large Skipper and Small Tortoiseshell.

Large Skipper (Ochlodes sylvanusbutterfly

Large Skipper feeding on flowers of Meadow Vetchling (Lathyrus pratensis)

Freshly emerged Ringlet butterfly (Aphantopus hyperantus)

This was also a great day for the Five-Spot Burnet moth; these are fantastic, chunky-bodied moths with underwings showing up bright pink in flight. They drone around on sunny days like florescent aerial tanks. I was chuffed to see the larva (caterpillar) and the pupal stage of the life cycle all in the same spot.

Adult Five-Spot Burnet moth (Zygaena trifolii)

The larval (caterpillar) stage - this one is probably close to pupating

The pupa (or cocoon)

Five-Spot Burnet moth (Zygaena trifolii)

Mating pair. Moths pretty much just do it in the open

I should probably warn you all now that there are more moth posts to come, plus references to hayfever, and BBQs... but never that it is too hot!

Tuesday, 2 July 2013

Death On Swift Wings

On a rare sunny morning in July 2012, almost a year ago to this day, I accompanied Tom Forward of Gatwick Greenspace Partnership on our first Gatwick bird survey. We had finished the transect and were walking back through the grasslands in the Land East of the Railway Line when we stumbled across this beauty (or perhaps beast)…
Death's-head Hawkmoth (Acherontia atropos)

Death's-head Hawkmoth (Acherontia atropos) about 13cm in length

A Death’s-Head Hawkmoth is a pretty unusual sighting in the fields around Gatwick Airport, or anywhere in the UK really! Again I was just obliviously stomping past when Tom (self-named 'Hawkeye' for apparently valid reasons) spotted this roosting in the grass. I didn't have a clue what sort of moth I was looking at (only that it was ridiculously huge) until he pointed out the obvious skull-like pattern on the back. On average only 2 or so are spotted in Sussex each year and a wingspan up to 13cm makes this one of the largest moth species to be found. They are common in the Middle East, African and Mediterranean regions and occasionally pass through Britain. 

Warning -  annoyingly excitable geeks feature in this video; feel free to mute.

The peculiarities do not stop at its appearance… when threatened this (extremely harmless) moth puts on quite a show, rearing up on its hind legs, lashing out with clawed forelimbs and displaying the bright orange colours of its abdomen. It also emits a loud squeak by expelling air from its proboscis. The caterpillar of this species feeds on the leaves of potatoes, the adults however raid beehives for honey at night, avoiding being stung by emitting a smell similar to that of bees. Cheeky.

The underbelly of the beast

The theory is that this individual was either a passing migrant or perhaps an escapee from a private collection. I'd like think it is the former; an intrepid explorer who's path we were fortunate to cross! 

Apparently there is even a limit to a Hawkmoth’s patience… tiring of our attention it began to quite literally hum as the large wing-muscles warmed up for take-off. A thrum of its wings and a spectacular flash of orange, we were left gawping as it flew a short distance and resettled out of sight in the long grass. This will certainly go down as one of our top natural history moments!