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.

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.

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.

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.

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.

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. 

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.