Dumbledor

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.

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.

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?

Mecca?

A dull East Bank, a great scrape; the Ruff and the smooth.

A weekend up in north Norfolk, the first for a while, brought on a bit of reminiscing as I walked around Cley, a place that, for a while, I seemed to visit nearly every weekend. I remember getting my newly published copy of ‘Where to watch birds’ back in the late 60’s and reading the following description of Cley:

“There can hardly be a serious bird-watcher in the country who has not made the pilgrimage to Cley. It has been the Mecca of ornithologists for the last 140 years...” wrote John Gooders, continuing ...”the East Bank at Cley is the best place in England to see passage waders – and to meet well known bird-watchers”.

I visited Cley soon after, on a YOC trip, meeting both Richard Richardson and Billy Bishop, but it was the couple of hours in the company of RAR on the East Bank that was truly inspiring as he seemed to magic birds out of thin air for us. My first solo trip to Cley was in 1970, and by chance, RAR was in a car that stopped for me as I hitch-hiked the final leg along the coast. The trip to Cley was to become a regular birding weekend over the following years and the walk around the Cley 'square' to became a favourite.  Many good birds were seen, with Caspian Tern, Red-throated Pipit and Black-headed Bunting amongst the better of my 'self-founds'.

Forty years on, Cley still delivers. Last weekend I saw plenty of passage waders (but there was a scarcity of well known birders, well, any birders in fact). Three Wood Sands, 2 Little Stints, Ruffs, Knot, Spotshanks, Greenshanks, numerous Dunlin, Whimbrels and godwits, and 9 Spoonbills were amongst the many birds on show. The scrapes looked in great condition, the hides blend nicely into the landscape and there’s a nice modern eco-centre containing a good range of books. I renewed my lapsed NWT membership, after all it’s only half the price of a tank of petrol.

But the walk around the ‘square’ is not what it used to be. East Bank is, well, dull, although Arnold's still produced as good a range of birds as any other pool. A bench has replaced the old flattened grass – and more than accommodates the number of birders there. A good walk should have points of interest along the way; variations in habitat, pools, openings, viewpoints etc, but those that previously existed, and the hides off the bank, have long since been removed or allowed to grow over.   Most disappointing of all, there is little sense of the history of this place. A few named hides or pools, and just a faded plaque for RAR on an obscure back wall. What could this place be like with a bit of imagination in both site layout and interpretation? This could be a birders Mecca, but currently it's just a well managed reserve with barely a nod to its past.

Returning home, I flicked through the pages of ‘Cley Marsh and its Birds’ by Billy Bishop and arrived at the page where he recalls a letter received from Lord Buxton in the 60’s. It seemed worth sharing. Lord Buxton writes:

“Within an hour I was sitting in the boat house watching a bittern boom – the very thing I had yearned to see for decades. But it was quite a shock. All the famous descriptions by experts were proved phoney. Quite honestly I was a bit embarrassed at first, because the bittern looked as if it was blowing off through its backside. This seemed rather a tawdry climax to the greatest discovery on earth and I wondered in what language I was going to announce it to the world!”

That Bitterns fart, rather than boom, is still a closely guarded secret.

Thinking and tinkering

One particularly energetic discussion with Dutch colleagues on the recent trip to The Netherlands centred around the qualities that make a good reserve manager. Why do some reserves appear vibrant and others as dull as ditchwater?

‘Thinking and tinkering’ is a phrase that may well sum up the best of reserve wardens . The great old wardens of yore ( and the best of today), were forever tinkering with their reserves; thinking about how to change things for the better and trying things out. Good reserve management requires an intimate knowledge of the site and an inquisitive mind. Reading through some of the books by wardens, such as Bert Axell’s ‘Minsmere: Portrait of a Bird Reserve’, this is clear. The now famous ‘scrape’ appeared bit by bit over at least 12 years. Trial and error was involved in getting it right, and much tinkering management by wardens and many volunteers.

Is this art of tinkering being lost? Perhaps. Nowadays, many wardens seem less connected with their reserves as the demands on their time increase and more time is spent behind the desk. Some even mutter about getting people in to monitor birds as they don’t have enough time!!   So how do we encourage the tinkerer? Well, partly it’s about appointing, and then developing, the right people in the first place, people with a passion for wildlife. However it’s done, we need more thinkers and tinkerers please.

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.