Trip reports

Slimbridge Trip

Slimbridge Trip
Doug Kelson

Tuesday, 19 March 2019

The long drive to Slimbridge was often through glorious English countryside, sparkling, spring-fresh, in the sunshine. Unfortunately, for much of the trip, that treasured scenery was muffled in a fug of fog. Just to remind me of what I was missing, there were occasional periods when the car breached into sunlight, bowling along, brightly, giving me hope that we would be able to see something at the end of the drive but soon it was back to fog-lights again and staring into the grey to find the faint, smeary, red glow that warned of rear lights on the car in front.

Despite the fog, I arrived early, intending to have a little walk before the rest joined me, to explore what might be seen around the local fields but the mist made that an unrewarding exercise. At least, I'd get to see birds close-to, in the reserve. From the car park, I could hear the Rooks being rowdy at their rookery, House Sparrows chipped in hedgerows and Robins trickled songs which had become less of a sad, wintry-warble but had developed spring urgency, stimulated by the unseasonably mild, weather lately. A single Stock Dove flew over the car park.

A clamour of clarion calls from unseen Bewick's Swans inside the reserve, perhaps on Swan Lake, reminded me where I was.

Members of Basingstoke RSPB Local Group began to arrive. There would have been twelve of us but one member seemed to have lost his way in the fog and diverted to Scotland (where he encountered a Tengmalm's Owl).

There was a rumour that the fog would clear, later in the morning. We hoped that would happen and entered the reserve. As we exited the buildings there were the Mute Swans and Bewicks of Swan Lake, to our left, sharing the space with Greylag Geese and a variety of familiar wildfowl. Though seeming relatively tame it must be remembered that the Bewick's Swans are wild birds which have made a long and hazardous migration from Siberia. They are in trouble and their numbers have dropped considerably, in recent years. This website:
https://www.flightoftheswans.org/meet/bewicks-swans/ gives a flavour of some of the problems encountered during migration. In 2017, the return, to Slimbridge, was confirmed, of a Bewick's Swan, named Croupier, at the age of 26. Unfortunately I haven't been able to find more recent news of him. Because of their unique bill markings and the numbered rings fitted to their legs, it is possible to identify each Bewick's Swan with accuracy. The fact that they travel in family groups means that it is possible to work out which others they are related to. These days, some are fitted with electronic devices which give precise details of their locations at all times. Because the study has been going on for so many years, generational relationships are understood. It is known if these generally monogamous birds have found new mates after some kind of "divorce" (it happens) or if a mate from the previous year has failed to turn up. It is easy to tell if a pair have managed to raise a family, or not, in any one year because the greyer, surviving young (if any) are with their parents, when they arrive at Slimbridge.

By the RBC Rain Garden, we watched a few wildfowl and a Male Reed Bunting which was industriously demolishing the spike of a Reed Mace, for the tiny seeds. Not far off, another pool had a thriving patch of Lesser Reed Mace. It was interesting to compare the two species and see just how much slimmer the seed heads of the Lesser Reed Mace are. I wondered why they were far less "exploded" than those of their larger relatives. Nearby, the thing to attract the eye was the closely-packed crowd of headless, one-legged Caribbean Flamingos. That was the first impression. Of course; a glow of pink/orange lumps in the mist atop a spindly forest of slim legs was sleeping birds. They seemed to be late-risers and were still resting; heads and necks wound down to the body. About their feet, a pair of the iconic Nenes or Hawaiian Geese shared the space. These were to be met in various parts of the reserve where a population remains, after Sir Peter Scott caused some, almost extinct in the wild, to be brought into captivity and bred, for later release into the wild, back in Hawaii, where they belong.

We decided to go indoors, for a while, where we could sit and see a few Bewick's Swans ghosting in and out of view through the mist on the other side of the glass. With careful peering, we were able to make out the elegant shapes of a few Avocets skimming their bills through water-surface at the back of the scrape. Shelduck, Pintail, Mallards, Greylags, Shovelers, and Black-headed Gulls emerged from the murk and disappeared again as they moved further off to "...fade to grey".

We wandered around the "world", for a while, visiting collections of waterfowl from Eurasia, North and South America; Asia etc. People were delighted with the chance to get a "proper" look at birds they might encounter in the wild, even in Hampshire. The scandalised "oos!" of Eiders were enjoyed by many; others got to see the golden eyes of Goldeneyes at close range and fully appreciate how these ducks got their names; it was possible to closely examine the intricate vermiculations on the backs of the likes of Lesser Scaup, Smew and others. It is just a pity that the much "fertilised", perhaps eutrophic water has such a thick cloud of disturbed mud and bloom of algae that it is impossible to see how diving ducks move under water.

I know the reserve uses bio-cleansing of the water which flows through; reed beds, for example but it must be quite a problem to keep water pooped into in by so many wildfowl in a healthy, clean condition.

A quick check through photos reminds me that I did what so many photographers do and concentrated on images of male birds but I tried to get pairs when I could. Like so many female birds, it is important that they be cryptically coloured when brooding the eggs. Redheads, though, may add their eggs to clutches of other species, at least, when young, and let them do the brooding. Fortunately ducklings forage for themselves so do not require feeding by a parent. Mostly, these birds are found in the lakes where they are supposed to be. For example; the Rosy-billed Pochard, from South America, is expected be in the Pampas Pen. Sometimes, though, birds, somehow, get into other pens and, always, they are likely to have free-loading Mallards, Moorhens, Coots etc. sharing their pools.

The otter exhibit proved attractive. These are the North American River Otters. They are used to coping with similar conditions to those we experience in Britain so are comfortable in an outdoor pen. In fact, weather in their natural range is often far more extreme; have you seen those wildlife films showing River Otters in the sweltering summers and deep snow of Yellowstone National Park, USA?). They are also more diurnal than "our" otters, making them a more interesting and reliably visible exhibit for the public to see. This trio romped, slid, swam and performed well, especially after the stimulation of being fed fish by the keeper.

Not far from the otters is Wader Shore. In this netted enclosure were fully winged Avocets, Black-winged Stilts, Ruff, Redshanks...and a House Sparrow. Again, this gave some birders in our party the chance to appreciate what may be familiar British Birds, (even the Stilts are becoming more regular vagrants which attempted to breed in Hampshire, in recent years) usually seen at distance through binoculars. A telescope is something many people don't fancy lugging about. When birds are seen well, as in this enclosure, it is easy to tell a Redshank from a Ruff and compare size and structure with other waders.

Another hide gave us views of crowded scrapes but most of the birds were still uncertain blurs in the mist. There were some Black-tailed Godwits, Dunlins, Redshanks, Golden Plover, a few Avocet, a single Snipe as well as a variety of other familiar wildfowl, for people to try their identification skills on in the trying conditions.

The group gathered at a kiosk near the north west end of the establishment, where most people seemed happy to spend money on food and warm drinks. These were best consumed under shelter. Next to the kiosk is a small, tall woodland. In its crown Rooks were raucously "conversing" and disputing with their neighbours. Despite the noise, it was possible, every now and then, to hear a gentle "thlip!" as something hit the dry leaf-litter, from above. A glance at the ground, starred with a galaxy of small, white splats, was all that was needed to explain that. Every now and then one or other of the Rooks would make a dry, rattling noise, almost identical to the drumming of a distant Great Spotted Woodpecker. Don't make hasty i.d. assumptions, if near a Rookery.

At one moment, there was a sudden crescendo of racket from the Rooks and a mass take-off. They wheeled around, joined by the many local Jackdaws. The "dread" didn't last long and the corvids returned to their activities. We supposed that a raptor had been sighted as it passed too near to the rookery for their liking but we didn't see one from our ground-based vantage point.

We had to run the gauntlet of the Rookery's short, soft shower of ...stuff, to reach more hides and screens. There were feeders hung from trees but they seemed to be attracting just Great and Bluetits, Chaffinches, a few Reed Buntings, Dunnocks, Robins and occasional Blackbirds. In two places, Water Rails were reported but few, if any of our group saw them. A water Vole was seen having a dispute with a Brown Rat, under a bird feeder. Spilt seeds are appreciated by more than just birds.

I know that there are great efforts to exclude mammals that might cause harm to the birds in the collection (just imagine what a Fox might do, if it got in) but I don't know what is done about the likes of Rats that might be inside the fences, already. The presence of Water Voles precludes the use of lethal traps, I suppose.

There were stops, in other hides, along the way, where we had, now that the fog was dissipating, good views of Curlews (and were able to hear their haunting calls) and some of the White-fronted Geese that are annual visitors to Slimbridge, associating with the Greylags on and around the pools. There were several Lapwings, elegant Pintails, rotating (or resting) Shovelers, occasional "plinking" Teal, Wigeon grazing Rabbit-mown turf, our only sightings of Grey Heron and Little Egret, of the day, another Snipe, a few foraging or resting Ruff, a few more Black-tailed Godwits and a trio of Roe Deer browsing along a distant hedgerow.

The main hide, has elevated, panoramic views of the grazing-marshes along the banks of the River Severn estuary. Reputedly, this can be a good vantage point from which to see the famous Severn Bore (pause for people to invent their own jokes and puns). The wave is sometimes powerful enough to wash over the banks, onto the grazing marshes we were looking at. Not due this day, though. Fortunately, it was not too crowded in the hide and we enjoyed searching for and viewing birds from our sheltered position, though many were fairly distant. Helpfully, most of the birds were relatively large and easy to see, especially now the mist had cleared.

Way over to our left, a far-off wooden gate was decorated with a pair of Peregrines. The smaller male seemed, at one moment, to root about in a cavity at the top of the gate post. Was it searching for left-overs it had stashed there earlier? Too distant to be sure. They seemed not to be causing any consternation amongst the other birds so were probably not in hunting mode at that time. Along the pleasingly scruffy hedgerows, a couple of Common Buzzards did little but loom. I imagine the rough grass of the hedge-edge offered the chance of something furry scurrying by; Vole, Mouse, Mole or Rat, even Rabbits are possible mammalian prey. The Buzzard is just as likely to pounce on a succulent earthworm, though. Another hedgerow provided a report of a possible Sparrowhawk, which dropped from the hedge, apparently to the grass and seemed to rise to perch on the far side of the hedge. This seems to be more the behaviour of a Kestrel but I didn't see the bird so cannot be sure. Any of the raptors described above, though, might have caused the disturbance witnessed in the Rookery earlier. Buzzards, in particular, are likely takers of young Rooks from their nests. I've witnessed this and I've also seen them take squabs from Wood Pigeon nests.

In the grazing marshes there was much activity, though the trio of Bewick's Swans preferred to hunker down and sleep. Maybe they were confident that the voices of the various geese grazing the grasses would alert them of any danger, in good time. Around shallow, temporary pools, Shelducks provided colour and a small flock of Barnacle geese trooped down to one of the pools for a break from pulling at the grasses. Further out, a gaggle of Canada Geese straggled over the grass. Small, brown shapes, hardly visible to people using binoculars, through the view-finder of a spotting 'scope became Skylarks chasing each other over the turf. The stars of the show, though, were the tall, stalking figures of the Common Cranes, wearing impressive bustles.

Slimbridge has been closely involved with the on-going re-introduction of these birds to this part of the country. There is a slowly expanding population of Cranes (a flock of 45 was seen there, recently) in East Anglia which may be of natural origin (though there is some controversy about this) but are certainly a self-sustaining wild population after many years breeding naturally, there. The ones we were looking at (and just about hearing) were mostly raised in captivity by people dressed in fake Crane costumes (to prevent chicks imprinting on humans) then introduced into the wild. This has been going on for some years and the birds are now beginning to increase their numbers by their own efforts. They are not yet "officially" British wild birds, though. We were told that one female, which succeeded in raising a chick, last year has found a new mate. He is unringed; of unknown origin, so, probably, a genuine wild bird, attracted to stay by finding a mate. In the rest of Europe, Common Cranes are migratory; grown chicks learning migration routes by following their parents but many British Cranes, it seems, are sedentary because our relatively mild winters allow them to find food in winter and they never learn migration from their parents: human or bird.

It might be quite a while, though before we can enjoy seeing flocks of many thousands, as they can, in (for example) Sweden and Spain, where I once saw a gathering of 50-60,000 Cranes.

I wondered how farmers would react to seeing a large flock of Cranes on their spring grain. An authoritative source gives this information: "Diet. The common crane is omnivorous, as are all cranes. It largely eats plant matter, including roots, rhizomes, tubers, stems, leaves, fruits and seeds. They also commonly eat, when available, pond-weeds, heath berries, peas, potatoes, olives, acorns, cedarnuts and pods of peanuts". Some items in this list are, obviously, not usually available in the UK. Others are not accessible to the Cranes (which don't dig) until exposed by humans. They don't take grain from growing barley, for example but will happily scavenge for spilt grain and exposed invertebrates in stubble, post harvest or left-over tubers and roots after the crop has been lifted. They famously search for acorns under Cork Oak groves in autumnal Spain and Portugal but will not refuse the chance of frogs, worms, locusts and much else. They are not generally regarded as problem birds.

These cavorting Cranes; leaped into the air; chased over the grass, stampeded through the Canada Geese and flew, using that distinctive slow down-stroke, rapid up-flick of the wings and bugling their metallic calls at each other. These were birds determined to put on a show!

Just in front of the hide, after the dramas out on the marsh, we were treated to a bit of tender romance, laced with comic relief when a pair of Jackdaws perched there. The male started to allopreen with the female, gently pulling her feathers through his beak to re-knit the ragged primaries. She, evidently, found this extremely pleasurable and seemed to enter an almost trance-like state, so much so that, when he abruptly stopped she found that the pull she had been bracing herself against was no longer there and fell off her perch! Only onto the next twig, a couple of inches below, though and she instantly recovered her composure.

We few remaining members of the group made our way back through the reserve and collection, stopping frequently to peer through screen hides, but seeing no new wild birds.

The sleepy Caribbean Flamingos we'd seen earlier (just one of six species on show in the collection) had found the brighter, afternoon weather much more to their liking and were now a lurid Phlamingo-phalanx, marching and milling in close formation and displaying; heads raised high, and wagging laterally at each other before dropping to briefly fake-preen. Next moment, up and wagging again, occasionally spreading black-tipped wings at ninety degrees. and all to a constant clamour of goose-like calls. A spectacular show. Why can I suddenly hear Val Doonican singing "Walk Tall"?

This website gives much interesting information about what could be seen in the collections and exhibits: http://www.slim-bridge.co.uk/

The website, below gives useful information on what was seen by others during our day there and suggests what we may have missed (some of the group did some wondering about away from the main group so may have different lists from the rest of us:

https://www.wwt.org.uk/wetland-centres/slimbridge/diaries/bewicks-swan-diary?page=3
"Diaries
24 Feb 2019
Fogged in for the morning
Posted on 24 Feb 2019
Thick fog hampered viewing so there was little to report until after 1230pm, Kingfisher, Treecreeper and Great Spotted Woodpeckers could all be heard in the 'pea-souper'. Thankfully, for those visiting, the fog lifted and another glorious sunny afternoon prevailed allowing everyone to view the wildlife.
Rushy Hide
43 Bewick's Swans were present at dawn with many lingering until they could see where they were going. O two were back in by 4.40pm, other tha the single bird on the Big Pen and three on the Dumbles, the rest were on the Severn. Last night three of the satellite transmitter wearing birds departed, two left together in a group of 12, by chance they were seen flying over the Wash in Norfolk by a member of WWT staff! It will be interesting to see if more leave tonight.
126 Pintail were at the feed this morning but very low numbers of Pochard and Tufted Duck remain, three Avocet were on the lower pond early morning.
South Lake
45 Avocets were reported late afternoon, one of which was ringed with two red darvics.
Holden Tower
11 Cranes and 130+ E. White-fronted Geese were among the Barnacle and Canada Geese, 5 Ruff and c40 Curlew fed in the tidal pools.
Tack Piece
A few Curlew and Redshank with 7 Ruff and a few hundred duck, most of which were Wigeon.
Willow Hide
Water Rail and Reed Bunting were seen here today"

At the end of my visit, I spent a pleasant half hour in the visitor centre, exploring "Toad Hall", seeing some fascinating amphibians, such as various colourful Poison Arrow Frogs, Tree Frogs, Yellow-bellied Toads, Alpine and huge, Ribbed Newts and Axolotls, among others.

Doug Kelson.