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.

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.

The poly and the plover

Ringed Plover (on Scottish machair), Grass-poly and a view across Moore Lake, Fen Drayton.

The week ended with a leisurely stroll around Fen Drayton lakes, a series of gravel pits adjacent to the River Ouse. This is a good site for wintering waterbirds, notably including Smew and Bittern, and now also supports a couple of ‘booming’ Bitterns and breeding Marsh Harriers. Fen Drayton is one of the very few remaining sites for Grass-poly, now classified as ‘endangered’ in the UK. The usual site held just one plant that I could see, but as I wandered around, many flowering plants were visible in a new location. This is a plant that requires disturbed ground with winter flooding and a spring draw-down. A programme of spring rotovation of plots should see it survive here.

The site also supports a selection of typical gravel pit waders; LRPs, Ringed Plovers and Oystercatcher, as well as Lapwing and Redshank. It was good to see a pair of Ringed Plovers with chicks. After their surge into inland sites in the late 70s and 80s, this seems to be a bird that is withering away as a breeding species in the south-east. The inland birds are now much scarcer and those on the coast struggle against disturbance and sea level rise. The latest national survey reported a 37% decline, with the greatest decreases in inland areas.

The key for both the poly and the plover at Fen Drayton is the retention of some typical early succession gravel pit habitat. Yet natural succession is usually rampant at these sites, and before long, all you have is a tree-lined pool of dullness, unless some drastic management is undertaken. Fen Drayton’s greatest asset is its location in an active floodplain. Floods from the Ouse can put the whole site under water but this makes the habitats more dynamic. Combining this with the actions of large herbivores and some periodic ‘knocking about’ with big machines (to create habitat at the right level in the flood regime) should see the value of the site being maintained.

Apart from the Ringed Plover, it was fairly quiet on the bird front. Lots of moulting Tufted Duck and Pochard, a Hobby or two, Dunlin and Redshank on muddy islands, and a family of Water Rails.