Thursday, 29 December 2011


Top two - Wallasea present.  Lower two - Wallasea future? (Tiengemeten)

A trip out to Wallasea Island in Essex this week reminded me of a visit to The Netherlands earlier this year. The Wallasea Island ‘Wild Coast project’ is a landmark conservation and engineering scheme for the 21st century, on a scale never before attempted in the UK. The aim of this project is to combat the threats from climate change and coastal flooding by recreating the ancient wetland landscape of mudflats and saltmarsh, lagoons and pasture. It will also help to compensate for the loss of such tidal habitats elsewhere in England.

Although the Wallasea project may be the largest of its kind in this country, the Dutch are ahead of us in this sort of restoration. In the summer, I visited the island of Tiengemeten in South Holland and had a glimpse of what Wallasea may come to look like in the future.  The project at Tiengemeten was undertaken as part of a programme to restore 3,000 ha of tidal areas in the Dutch Delta region, itself part of the wider Dutch Ecological Networks Plan to create 160,000 ha of ecological networks. Tiengemeten extends to 1,000 ha and was formed as agricultural land claimed from saltmarsh. Now it is being returned to near-naturally functioning habitat. The island has been divided into three zones. The Wilderness zone covers 700 ha and is ex-arable land now open to the influence of the tides and water regimes of the island. The Richness zone (250 ha) is a landformed area of shallow flooding, reedbed and scrub, wet in winter, drier in summer. Finally, the Cultural zone (50 ha) is made up of a campsite, a cafe and a few houses and cropped fields. Grazing by Highland cattle is the primary management tool.

The island was officially given back to nature in 2007 after it was purchased by the Dutch Government. In 2008, a full breeding bird survey was undertaken. The results included the following totals (pairs): 87 Bluethroat, 125 Avocets, 4 Black-winged Stilts, 151 Marsh Warblers, 18 Black-tailed Godwits, 11 Garganey, 3 Spotted Crakes, 3 Goshawk, 1 Corncrake and 612 Greylag Geese. Another full survey was undertaken this year and the results are awaited with interest.

Meanwhile, back on Wallasea, the landscape is still of arable fields surrounded by sea walls, and it has a way to go to match Tiengemeten. Despite this, the birding provided some anticipation. Thousands of Brent Geese and Lapwings fed in the fields. Hen Harrier, Marsh Harrier, Merlin and Peregrine hunted around the sea walls or over the areas of un-harvested crops retained to provide food for farmland birds. A single Rough-legged Buzzard and a Spoonbill provided the highlights for the day.

Saturday, 24 December 2011

Fishy pits

Pike and crayfish sushi appears to be on the Christmas menu of the Great Northern Diver currently residing at Nazeing gravel pits in the Lee Valley.  A largish crayfish brought up from the depths was dispatched with some skill.   Nazeing is not the most exciting of the valley waters for the birder but being one of the largest of the gravel pits, it does occasionally specialise in stray seabirds.   Black-throated and Red-throated Divers have made long-staying appearances, as well as visits by Velvet Scoter, Long-tailed Duck and Fulmar.  In the dim and distant, a Little Bittern was also seen, not that there’s much habitat for it today.  Prior to the 1970s, Nazeing held huge numbers of diving duck, mainly Tufted Duck and Pochard.  Numbers declined sharply and remained low until recent years when numbers have increased again, probably due to reduced disturbance as the amount of sailing has declined. 

The lack of aquatic vegetation, either submerged or marginal, results in minimal numbers of herbivorous wildfowl, even Coots are remarkably sparse.  However, fish populations are good, as evidenced by the numbers of Great Crested Grebes (usually up to 50) and Goosander (20+ at peak).  Nazeing is currently one of the best sites for Goosander in the valley, with the last 15 years seeing a significant shift in Goosander distribution from the Lee Valley reservoirs to the gravel pits.  The size and openness of the lakes attract passage terns and gulls.  The northern lake intermittently supports a small gull roost; in the past with up to 10,000 birds nightly, mainly Black-headed and Common Gulls, with the occasional Med Gull.  When spring tern passage is underway, a quick check is often productive.  If Arctics or Blacks are about, there a fair chance Nazeing will pull one.

Saturday, 3 December 2011

An Eastern Crowned Warbler once flew halfway across this ride

....and into a whole net of controversy. And who’s fault was it that we didn’t see this eastern gem – well it was everyone’s apparently, although no-one seemed to blame the warbler for flying off. It was apparently released into a willow tree, with barely a good-bye, but at that time it was just a Yellow-browed Warbler, low-life amongst asian vagrants, barely worth the time of thinking ‘not a bad inland record’ let alone travelling to try to see it. Then its true colours were revealed (good job they didn’t have to send the prints off to Kodak) and the greyness of its crown matched the blood-drained faces of the local birders who suddenly realised Hertfordshire’s one-in-20-year-good-bird was at Hilfield Park Reservoir, otherwise known as 'Fortresss Hilfield'.

There was some talk that some didn’t want the news to be released. Now if ringers or birders don’t want to release news of a bird, that’s their decision as far as I’m concerned. One might argue it’s a little anti-social as there can hardly be any birder who hasn’t at some time gone to see a bird found by someone else...but it is their decision and should be respected. I’ve nothing against ringers either, quite the contrary. Did you know that, statistically speaking, 50% of the UK’s recorded Eastern Crowned Warblers have been picked out of a net. However, this was Hilfield Park Reservoir – a designated Local Nature Reserve (LNR), and according to Natural England “LNR’s are for both people and wildlife”.

The trouble is, I’m not sure how many ‘people’ are thought should benefit from an LNR, but it surely must be more than the present number, and it would certainly include the hastily formed Hertfordshire branch of the Eastern Crowned Warbler Appreciation Society (ECWAS). Okay, so the birds of the site are well recorded and documented in an excellent report (where you can see that the site doesn’t actually have many ‘crowning’ moments). There is a view that withholding bird news is in the best interest of the conservation of the site. But ultimately is it really beneficial for the future of the site?

Back in the early 1990s, the Wildlife Trust stoutly defended this site against a planning application to locate the nearby sailing club on the reservoir. Had it lost, the site would not support its current importance for wildlife. One of the main arguments used at the time was that the site was not fulfilling its LNR objective – ‘for both wildlife and people’, as few people were allowed in. Now this is a water company operational site and understandably there are rules to be followed. Anyone can access this site if they are a Wildlife Trust member and arrange to pick up a key (as it has always been). But opening the site for special events requires a bit more organisation and supervision. And by the time the ECWAS arrived, it was apparent that the warbler’s discoverers had scarpered as quick as the bird itself. Perhaps if the spirit in which the site was designated is to be fully realised, a ‘friends of...’ group, with a specific remit to both record wildlife and ‘encourage use of the site’, might be a better bet for the future.

Thursday, 10 November 2011

Old and new

It’s interesting to compare sites and over the last week I’ve looked at the development of some new sites and the problems on some old ones.  The new included the still rather raw Frampton Marsh in Lincolnshire, where the scrape habitats, once fully functioning, promise to be amongst the best in the country.  A murky day delivered a Black Brant amongst hundreds of Brents, a Great Grey Shrike, Hen Harrier, Blackbirds and Fieldfares dropping in from a grey sky, and a plate of Blewits for supper.  A day later, the early signs of a diverse habitat of reedbed and heathland were evident at Snape in Suffolk, with young, vigorous reed romping across the re-wetted valley.  The old sites included North Warren, where a Dusky Warbler tacked away in the bushes and the first White-fronted Geese of the autumn dropped in, and, a few days previously, Leighton Moss in Lancashire, where my undoubted highlight was a Great White Egret flying behind a Marsh Harrier circling over a feeding Otter, although roosting waders on the saltmarsh pools was not far behind.

The loss of breeding Bitterns from the reedbed at Leighton Moss has been a cause of some concern and debate.  The fundamental problem at Leighton (for Bitterns at least) is that it is an ageing reedbed.  Reed die-back around the meres has been noted for many years, with a recent replacement by Reedmace.  Reed die-back is a well known issue in older reedbeds, resulting in poor quality reed with a low genetic diversity. The formation of toxic by-products by the reed litter under anoxic conditions reduces shoot density and vigour.  Reed re-colonisation into anoxic sediments is also known to be poor. At Leighton, the grazing effects of both moulting Greylags and numerous Red Deer are likely to be a significant contributory factor.

We know that fish biomass is way above the accepted threshold levels for Bitterns and that eels are as abundant as at any site.  The site supports several wintering birds yet the one remaining boomer is of poor quality and a late starter.  This all strongly suggests that a lack of fish availability in the reed/water interface is preventing birds reaching breeding condition, with a lack of secure nesting sites due to the drier conditions an additional problem for Bitterns.

However, Leighton Moss remains a superb wetland habitat with a high species diversity.  Old age results in one or two little grumbles but overall the quality shines through.

Saturday, 29 October 2011

Island Mere in ruddy health

Rudd (top), Roach and the new Island Mere hide.  Note head shape and mouth structure of the fish.

Electro-fishing the Island Mere at Minsmere usually has to be a quick affair so as not to upset too many visitors. However, this week it was more leisurely as it is closed to visitors while a new island mere hide rises from the marsh. The hide traditionally provides excellent views of Bitterns on the edge of the mere and it was along these margins and in the adjacent ditches that we concentrated the fishing effort. The results were spectacular – an estimated fish biomass of 74 kg/ha - one of the best recorded at Minsmere. Roach formed the bulk of the biomass, but with significant increases in Rudd and Perch. Tench, 3-spined and 9-spined Sticklebacks made up the remainder of the catch.

Research has shown that Rudd are a major food source for breeding Bitterns whilst Roach are less important. Why should this be for two apparently similar fish? The answer probably has to do with differences in their behaviour. During the daylight hours of the summer months, Rudd tend to hide amongst the reedy marginal vegetation, thus making themselves easier to catch by Bitterns. By contrast, Roach spend more time out in the open water amongst weeds and away from the margins. However, in the winter months, both species move into deeper, more sheltered ditches and Roach are likely to be more available to feeding Bitterns. Given good water levels in the spring, the signs are good for breeding Bitterns next year.

Earlier in the week, on another site, I looked at the nesting site of a pair of Cranes. They can be remarkably secretive in the breeding season and tend to choose a secluded nest site surrounded by shallow water. The nest often looks out over a small clearing in the wetland where they can see the approach of predators. This particular nest clearing is growing over fast and work will be required this winter to open it up a little. However, whilst the young chicks will feed around the nest, it is the quality of the wider foraging area that will determine the likelihood and speed of the chicks fledging. Invertebrate-rich, tall vegetation, preferably in wet (squidgy) conditions is a key requirement.

Friday, 21 October 2011

Shingle session

Twite, Purple Glasswort and Sea Pea.

The coastline between Dunwich and Walberswick in Suffolk supports some excellent shingle and lagoon habitat. Yesterday was spent wandering around the Dingle Marshes thinking about some of the key issues. Sea level rise is a major threat to this stretch of coast and recent inundations have pushed the shingle back, creating some great looking habitat for Little Terns and Ringed Plovers, or it would be but for the heavy disturbance in this popular holiday area. The remains of Sea Pea and Sea Kale were evident but such specialist shingle plants are also suffering from trampling.  Almost the first bird I saw was a Glossy Ibis, flying up from one of the pools and disappearing over the ridge towards the Walberswick reedbeds. However I spent rather longer watching some more typical winter visitors – a flock of 16 Twite feeding where the shingle meets the saltmarsh.

Twite wintering on the east and south coasts of England are thought to be mainly, or entirely, from the small south Pennines breeding population. It is possible that small numbers of Twite from Norway also winter in this area, although no Norwegian-ringed birds have so far been recorded in the UK, despite the large numbers ringed in Norway. The number of Twite wintering on the east coast have declined substantially over the last few decades. Flocks of thousands were noted around The Wash back in the 70s and 80s but now the latest estimates are of no more than 450 birds between the Humber and Kent. The Dingle/Dunwich area remains the main locality in Suffolk. Wintering Twite feed on the seeds of Glasswort, Annual Sea-blite, Sea Lavender and Sea Aster, with late winter distribution shown to be strongly related to the density of remaining Glasswort seeds.

Half a dozen Spot Shanks, several Greenshank, Knot, Dunlin and Grey Plover fed around the shallow lagoons behind the beach with a number of Rock Pipits and at least one Water Pipit. Redwing, Fieldfare and Siskin calls constantly reminded of small parties passing overhead. A Red Kite drifting south completed a reasonable morning.

Monday, 3 October 2011

Passed glories

 Broadhurst Clarkson 4-draw - my first 'scope, Wood Sands on condom island, Rye Meads 1984.

With unidentified stints seemingly on every patch of mud in the country, I decided it was time to check out the Valley’s wader hot spots. Unfortunately I was 30 years too late. Remember the good old days, when you could pop down to the local sewage works? You crept up the bank and positioned yourself in a bed of nettles, 4-draw scope balanced on your legs, watching the pool of deep brown, bubbling and steaming liquid, with condom-encrusted muddy islands dotted with Green and Common Sandpipers and waiting for a Ruff or two to drop in?

The Lee Valley had a string of such sites, Rye Meads, Broxbourne, Rammey Marsh, Ponders End and Edmonton (Deephams) at least. G E Lodge ‘discovered’ the Lee Valley sewage farms as early as 1900, recording at Edmonton and Ponders End. He found the first nesting Ringed Plovers in the London area in 1901 and was recording Dunlin, Greenshank, Black-tailed Godwits and Ruffs, via his shotgun, around that time. Much later, London’s sludgy gems at Perry Oaks and Beddington were ‘discovered’, the former by Lord Hurcomb in 1946 (who once asked to look through the very scope in the picture to view a distant wader).

Rye Meads was the first sewage works that came to my attention, after the appearance of a Solitary Sandpiper in 1967. It was one of those secret places surrounded by high chain-link fences and barbed wire, where birding news only slowly crept out when everything had gone. I still find it difficult to go through the gate of that place. I’d much rather look for a hole in the fence or catch the seat of my trousers as I scramble over a weak part of the defences. Other sites in the valley were located by searching the Ordnance Survey map for the magical word ‘works’, followed by a recce to find a weak spot around the perimeter. Once in, creep up the bank through the ten foot high nettles, peer over the top and hope for sludgy goodness covered in waders. And further afield, who will forget the birding experience of watching at Wisbech when the shit lorry arrived and disgorged. It always seemed to make me feel hungry for some reason. Conveniently, there was usually a fine crop of poo passed pip tomatoes growing right in front of you.

Sadly such places are all but gone, lost to modern techniques. In theory, we could re-create such places if we all made a ‘contribution’.

Below - Rye Meads 1986, Deephams 1985. 

Saturday, 1 October 2011

Magnam swirls take shape.

Heard of Bowers Marsh yet? No? Believe me, if you are a birder, you will do before long. I was back down in south Essex yesterday to look at the continuing development of this new RSPB nature reserve. This massive habitat re-creation project aims to create a range of dynamic, salty to fresh, wet to dry, Thames-side habitats. I have previously blogged about Bowers at an earlier stage of the work. Now the diggers have done most of their work and some areas have started to ‘settle down’. Compare the top picture here with the same view below. Avocets have already moved in and bred on the new ‘creek’.

The new 20 hectare scrape will also function as a reservoir for the grazing marsh habitats; brim full in winter but releasing water through the spring and summer to keep the marsh wet. Today the contactors carefully placed a ‘topping’ of sand and gravel on the islands constructed within the scrape, but how do you explain to dozer drivers how you want the mix spread? Well, I pondered, bit the top off my ice cream (it was a warm day), looked down, and said “We need to create intimate swirls of differing substrates, from sand to chocolate, sorry, I mean gravel”. And so the Magnam swirl island was conceived.

This week, the first tides surged onto the new saline lagoon. The lagoon will eventually support a mix of mud flats, saltmarsh and islands. Tides will flow on daily to controlled levels. Gulls seem to like the new habitat; Meds and Yellow-legs mingled amongst the hundreds of Herring and Lesser Black-backs.

Wednesday, 21 September 2011

Scrapes, plums and flaming O's

Probably not the most popular person yesterday as I collected samples of invertebrates from the scrape at Minsmere.  A flurry of birds and all were gone - apart from a couple of tame Pec Sands and 'Fiona' the Flaming O.  The invertebrate samples will help inform management, providing further information on the food resource available to birds in water of differing salinities.  More on this when the results are in.  A couple of Whimbrel and a fly-by Curlew Sandpiper added interest.

Back onto the path and the scrape-side bushes were dripping with ripe plums. There seems to be a bewildering array of ‘wild plums’ to be found in our hedgerows. Fruits of differing sizes and ranging in colour from yellow and red through to purple. The plum is thought to be the result of hybridization between the Sloe Prunus spinosa and the Cherry Plum Prunus cerasifera. Such hybrids and an array of back-crosses fall under the Wild Plum Prunus domestica heading, with various forms or subspecies. These late-ripening fruits at Minsmere seem to fall into the 'Bullace' category (P. d. insititia).  In a minute or two, enough were gathered to produce a tasty Wild Plum Frangipane - just like this.

Friday, 16 September 2011

Extreme vis-migging

Lower pic - the Lee Valley from Tower 42 - Walthamstow, the Girling, the George and beyond.

I’m not keen on heights but as Tower 42 is now only the 5th tallest building in London, at 600 feet, I thought I’d give it a go. We clambered up various steps and ladders onto level 47, the very top, with a splendid all-round view of London for a session of watching for visible bird migration over the city.

Everything looks very small from up there!  No doubt, the more eyes looking the better, but in 4 hours we recorded the following: 22 Lesser Black-backed Gull, 4 Buzzards, 3 Kestrels, 4 Sparrowhawks, 2 Peregrines, 5 Cormorants, 1 House Martin, 10 Swallows, 1 green balloon, 1 blue balloon, 1 Tesco bag and 5 flies.

An excellent morning that showed the potential if you could hit the right day. Many thanks to David Lindo for organising it all (as detailed here) and to the tolerant Tower 42 security guys for putting up with us.

Tuesday, 13 September 2011

Chipirones and carrots

The top priority as we pulled into Sant Carles de la Rapita was a plate of chipirones (fried little squid) and a cold beer. A plate of razor clams drizzled with oil and lemon soon followed, oh and some octopus 'a la plancha' of course. Several hundred Swallows moved south past the front of the harbour-side bar as we swallowed. The first of many Audouin’s Gulls drifted by. Another plate of chipirones? So started our weekend seafood extravaganza in the Ebro Delta in Spain.

After a long lunch we drifted out into the delta to work up an appetite. Rice fields everywhere; the wet harvested areas full of egrets and herons. Most of the delta is now given over to rice production but there are a few protected areas of wetland (but many are privately owned by hunters) that support tens of thousands of waterbirds. The brackish La Tancada lagoons held 300+ Greater Flamingos and many passage waders; Little Stints were everywhere and Kentish Plovers dotted about.

L'Encanyissada is a large shallow freshwater lake surrounded by reedbeds. Hundreds of duck, including Red-crested Pochard, and another 200+ Flamingo formed the main birdy backdrop. At least 150 Whiskered Terns hawked back and forth along the margins or perched on every stick that stuck out of the water. Little Bitterns and Squacco Herons flew hither and thither. A flock of 8 carrot-beaked Caspian Terns arrived in front of us. As dusk drew near, Night Herons appeared miraculously all around and straggling flocks of Purple Herons rose out of the reeds. Stomachs began to rumble. We were soon into the main event; sucking the juicy brains out of Mediterranean Red Prawns, slurping more clams out of their garlicky shells and working through a huge pot of mixed fishes in fishermans sauce thickened with a garlic and almond picada. Yum. A fine Rioja eased their passage.
The following morning we headed out to Riet Vell, where the SEO (Spanish Ornithological Society) have a site than produces organic rice. The harvested fields were left wet and held many waders; Temminck's Stints, Wood Sands, Curlew Sands, Greenshanks and LRPs were the most numerous. A quick look from the hide overlooking the reedy lagoon resulted in an eye to beak meeting with a Purple Gallinule.

Zig-zagging through the rice fields we arrived at El Garxal lagoon. Hundreds of terns (Common, Little and Sandwich) congregated along the shoreline, along with more Whiskered and another couple of Caspian Terns and many Med Gulls. Three flocks of Glossy Ibis, totalling around 200 birds, arrived off the sea and headed inland. Fan-tailed Warblers zitted up and down and Sardinians rattled. A Praying Mantis obliging sat on my finger, wondering if I looked like dinner. Dinner did you say? We eased back to a restaurant on the edge of some marshland. Is that a Moustached Warbler in front of those Penduline Tits? Never mind, here come the langoustines with green beans and basil (steady, that's enough of the vegetables), then the clams, the smoked eel and yet more crispy yet succulent chipirones.

Swallows continued to flood south, now joined by increasing numbers of Sand Martins, as more seafood headed in the same direction, washed down with a nice chilled Cava. More Audouin’s Gulls floated by. Sea Cucumbers anyone? A great weekend, shame we didn't have more time, I didn't try the oysters.

The full list:
Squid, cuttlefish, octopus
3 species of prawn
4 species of clam, including razors and tellins
A spikey-shelled whelky-type thing
Hake, sole, monkfish, salt-cod, anchovies, sardines, fried baby fish.

Wednesday, 7 September 2011

Omophron beach

A good day: Omophrons, Lycopodiella, Bog Bush-cricket and Nike Air.

Mark, normally a docile sort of ecologist, has taken just a few paces onto the site before he kicked some water up from the small lake onto the adjacent sandy beach. The peace and quiet was broken by "f*****g hell" repeated 24 times at high volume. A small green and brown beetle looked up, wondering what the fuss was about. So started a visit to a new site for both of us, a redundant gravel pit in north Norfolk.

The beetle in question was Omophrons limbatum, a rare beast of bare, sandy freshwater margins with fluctuating water levels, previously known only from the Dungeness/Rye area and the Norfolk/Suffolk border. The gravel pit had tumbled back to heathland since excavation and looked worthy of much more scrutiny than we had time to give it. Looking up from the beetle, we noticed Sundew colonising the lake margins. Nearby, another local rarity, the Marsh Clubmoss Lycopodiella inundata was noted, probably at only its second Norfolk site. Up into the heather, and Bog Bush-cricket was added to an ever growing list of scarce species. Who says gravel pits are dull.  Nearby, Nike was announcing a new eco-range.

Monday, 5 September 2011

Ouse Fen comes of age (what a tinca!)

Ouse Fen from the air and at boat level; a stunning Tinca (Tench) and a not-so-stunning stickleback

Amongst the headline figure of 104 booming Bitterns in the UK this year was the smaller milestone of the first successful nesting of Bitterns at Ouse Fen (Needingworth Quarry) in Cambridgeshire. The partnership project between Hanson and the RSPB will eventually become Englands largest reedbed as the habitat is created following gravel extraction.  A day spent reviewing progress was very instructive. The aquatic habitat in the developing reedbed compartments looked superb, with abundant aquatic weeds including the scarce Fan-leaved Water-crowfoot and Hairlike Pondweed.

A search for the now redundant Bittern nest was easy enough, thanks to excellent triangulation by the guys recording the birds activities during the long watches required to prove breeding. The typical small woven platform of reeds was constructed in what would have been about 60-70 cm of water at the time. All the feeding flights were from the nest location across to ‘Phase 1’, the oldest reed compartment. A further couple of hours of electro-fishing provided the reason for this. The relatively young area of habitat around the nest has few fish as yet, just a few sticklebacks, but the more mature compartment supports a respectable fish biomass of around 21kg/hectare, mainly Perch and Roach. This is above the 10kg/ha considered to be the threshold for successful Bittern breeding. So why did she not nest where the fish were? The simple answer is that the dry spring had reduced water levels in the reeds in ‘Phase 1’, thus reducing the security of any nest. However, the story is even more complicated. There were no booming males heard at Ouse Fen yet there was a nest. At nearby Fen Drayton, there were 2 boomers yet no nest. It is likely that the dry spring also affected the reedbeds at Fen Drayton and as a result the female moved across to the wetter Ouse Fen to find a secure nest location. Thus she found a mate, a nesting site and a food source in three different locations.

The electro-fishing also produced a few Tench; surely one of the most stunning of our freshwater fish with those golden scales. Less visually attractive, although interesting in a rather gruesome way, was the high parasite load of the Nine-spined Sticklebacks. The photo above shows one poor specimen with a bulging abdomen containing a Schistocephalus tapeworm (S. pungittii is the usual species in this stickleback). If that wasn’t enough it also has myxosporidium cysts (a protozoan parasite) to contend with.

Family parties of Bearded Tits (one of three) and Marsh Harriers were additional evidence that this new site is coming of age. A single Garganey, a few Little Egrets and several Hobby all helped round off a pleasant day in a boat.

Wednesday, 31 August 2011


A couple of days looking at habitat management for invertebrates last week focused on providing for their often complex life histories. Whilst poking around in cow dung, as you do, this chap, the Northern Dor Beetle or Dumbledor, Anoplotrupes stercorosus, trundled by. These dung beetles are usually to be seen carrying mites around their bodies and it is perhaps an easy assumption that these mites are parasites on the beetle. The truth, apparently, is far more complex. The beetle excavates a burrow and provisions it with fresh dung before laying eggs in the burrow. The beetle then leaves some mites behind, as they eat the growth of fungi that would make the dung mouldy and thus inedible for the developing beetle larvae. The beetle and the mite thus both benefit; a fine example of mutualism.

J K Rowling apparently chose the name of the Harry Potter character as it is the old English name for bumblebee and she imagined the "wizard humming to himself a lot". Dumbledor is also one of the common names for this splendid beetle, but I guess she didn't imagine him rolling around in shit.

Tuesday, 30 August 2011

Pickled walnuts

Okay, so a brief diversion to another great passion of mine - food, especially if it’s obtained free of charge whilst out in the countryside. On a visit to darkest Essex a month or so back, there was little to do other than stare up into a walnut tree pondering the unripe green nuts and wondering why the visit hadn’t been arranged for later in the year. “You could pickle them” said Jon.

By the time I arrived home, I had stopped at three random walnut trees and gathered a bucketful. Now I have 20 years supply of pickled walnuts, probably the best thing about Christmas. And this is how it happened.

Wednesday, 24 August 2011

Salty or sweet Sir?

Redshank, Black-tailed Godwits, Ruff and Dunlin feeding on the lagoon at Conwy as the water drops to a suitable feeding depth; Ragworm or bloodworm, which looks tastiest?

At what salinity should coastal lagoons be kept to maximise bird use? Coastal lagoons have a salinity that will vary between seawater (at 35 parts per thousand (ppt)) and fresh (1 ppt). The salinity will influence the invertebrates that dominate the lagoon and therefore the birds that are found there. This week I visited Conwy in north Wales where a proposal to change the lagoons from fresh to saline is being considered. How might this affect the birds that feed on the lagoons?

Low salinities (less than 8 ppt) will favour non-biting midges (chironomids) in the mud, with water boatmen (corixids) and opossum shrimps in the water. At higher salinities (8-40 ppt) ragworms Nereis and mud shrimps Corophium will join the chironomids and the shrimp Palaemonetes varians may be abundant in the water. The maximum biomass of the chironomid/corixid and ragworm/shrimp fauna will occur at about 6 and 24 ppt respectively.  However, the other key factor for attracting birds is the water level.  Good numbers of birds will only occur if the prey items are available at suitable water depths so good control of the water levels is desirable.

At Minsmere, various parts of the scrape are kept at different salinities; North Girder (in front of South Hide) at 15-35 ppt, whilst East Scrape is usually less than 15 ppt. The freshest scrapes (eg West) can become dominated by aquatic vegetation such as Mare’s-tail; an occasional dosing with salt water will sort this out. Switching between high and low salinities will kill off invertebrates. However, most of the less specialised invertebrates can re-colonise rapidly. Such switching may be useful as an occasional management tool but not on a regular basis.

The excellent scrapes at Cley are fed by fresh water draining from higher land, and are usually less than 1 ppt. However, high tide surges can bring an incursion of saltier water. Vange Marsh in south Essex, a seriously good addition to the scrape world, is also kept at a low salinity, usually less than 5 ppt, attracting sandpipers, shanks and godwits.

Last Friday I was at Havergate Island, where the lagoons support scarce lagoon invertebrates such as the Starlet Sea-anemone. Here the invertebrates rather than the birds determine the water regime as the salinity needs to remain in the favoured range of 25-40 ppt for these lagoon specialists. The lagoons did however, hold hundreds of birds, including 14 Spoonbill, 350 Avocets as well as numerous Knot, Black-tailed Godwits, Dunlin, Grey Plover and Redshank.

Below - How many Starlet Sea-anemones can you see?