Bontuchel

Visiting Nain, the bird-feeders are going incredibly well, Blue, Great and Coal Tits, Robins and at least one Nuthatch. Also Mice.

Nuthatches are amazing looking birds with very sleek grey backs and warm peachy undersides. They also have long vicious bills. According to the RSPB, the birds seldom travel far from the woods where they are hatched, so the one in Nain's garden may have come from the woods around the Woodlands or perhaps from those on the other side of the valley (average distance of ring recoveries are less than a kilometre away from their ringing site). They will take food from bird-tables and secrete it around their territories, which are held throughout the year. They are unique among UK birds in plastering mud around their nest-hole entrances (eh? House Martins?)

They are found across most of England and Wales, and now just into Scotland, forming a population of about half a million birds altogether, with numbers steadily rising since the 1970's - perhaps due to increasing use of bird-feeders. It will be interesting to see if ring-necked parakeets compete vigorously with it for nest sites, and have any impact on its numbers in the future.

Their hoarding habit is long term - three months or more, and the hoarded food is used strategically, mainly in periods of severe food shortage, and rather less in more benign weather.

Shellness with Dark-bellied Brents

A slightly gloomy typical Sheppey long afternoon at the end of the day on a very high tide.

The fifty or more Brent Geese were happily vocalising just offshore, exploring backwards and forwards. There were one or two birds in every dozen that I thought were youngsters - unclear or very limited white neck collars - e.g. lines rather than triangles, and the flanks more evenly grey, rather than diagonally streaked pale and dark. Even as they lose these juvenile markings first-winter birds may still retain the juvenile pale tipped coverts on their backs, although even these gradually fade over the winter (Clausen et al, 1998). They are all such beautiful, if nearly monochrome, birds.

Turnstones explored the shelly beach, often well up from the waters edge. I was closer to these than any of the other birds, and they were really lovely!

Grey Plovers were perched here and there - for example on the groyne pillars just poking out of the waves. Later as the tide peaked (?) battlegroups of Grey Plovers skimmed past from the direction of Muswell Manor to the North, and settled close to the blockhouse. They gave me a very musical send-off when I left.

Again as the tide peaked I suddenly noticed about a hundred Curlews on the grazing marsh - before a passerby flushed them off out onto The Swale.

On the spit beyond the blockhouse, hundreds of Oystercatchers and dozens of Great Black-backed and other Gulls were roosting. Three or four Common Gulls, Larus canus, were seen floating just off the large glass-fronted house.

A Pied Wagtail searched the tideline.

The day finished off with a colourful sunset over the wide horizons of Sheppey, as I bumped over the ruts picked out by the headlights back to the tarmac.

I looked back at the older posts in this blog and thought about the variations in breeding success, juvenile plumages, and feeding habits of the Brent Geese noted there. I do love these geese! I also had a look at the scientific papers relating to the species. It was interesting to find a 2001 paper by McKay et al., recommending Clover as a suitable "Alternative Foraging Area" or "AFA" to tempt the geese away from winter wheat where they can cause a lot of damage. However, I thought Clover looked a bit like fast food, its growth can be very variable in different seasons according to the weather (it is "notoriously unpredictable), and therefore perhaps should not be entirely relied upon.

An alternative is grass regularly cut short, which is normally low in fibre and therefore rich in Nitrogen, although in trials by Rillington et al., 1995, in Southern England the geese show preference for, and benefit from longer grass if Nitrogen fertilised, a situation which should have a greater carrying capacity. However Nitrogen fertilisation does have environmental side-effects, and will be inappropriate in many situations, perhaps requiring an environmental derogation for the sake of the geese. Another point they made was that disturbance while feeding on land was potentially highly disruptive, frightening the geese off their pastures.

Hassall and Lane (2005) working in Norfolk argued that the geese are constrained both by nitrogen limitation and perceived mortality risks. For most of the season they exhibited partial feeding preferences by feeding on two or more types of food each day. They fed on salt marsh plants throughout the entire wintering season. In addition, from October until March they fed for part of each day on supplementary sites that were more profitable for nitrogen. In October they fed first on intertidal algae, the most profitable source of nitrogen. When this became depleted in late autumn, they moved inland to feed initially on winter wheat, where they were subject to control shooting, then onto pastures. By mid-March the pastures were no longer a significantly more profitable source of nitrogen. The geese then switched to feeding only on the salt marshes at a cost of a 39% decrease in their overall assimilation rates.

It was very interesting to see that ancillary evidence gathered in Rillington's paper also suggested that the geese on the land preferred fields with low hedges, unimproved, proximity of the sea, and no roads or footpaths. This does sound a bit like the fields at Reculver which the geese use. However at the moment, early in the winter and soon after their arrival, they still seem to be focusing on feeding on algae, etc, on the sea and in the inter-tidal zone.

The move to feeding on agricultural fields is thought to be an indirect result of historic population increases to previously known levels. The traditional wintering habitat is mostly shallow coasts and estuaries with extensive mudflats and intertidal areas, as Dark-bellied Brent Geese rarely occur far from the sea and feed on intertidal plants such as Zostera, Enteromorpha and a small range of littoral plants. Population growth during the 1980s resulted in more rapid seasonal depletion of natural food
sources. Thus, since the late 1970s, the geese have adapted to use coastal grasslands and the
early growth of cultivated cereal crops (van Nugteren 1994; Ebbinge et al. 1999). However how the populations prior to the 1930s and in the nineteenth century (and possibly earlier) managed without modern autumn sown cereals and winter pastures is rather a matter of guesswork.

Clausen et al.,  (1998) working in Denmark and NE England with the small Light-bellied Svalbard population, showed that in some years with apparently colder winters there were substantial losses of the first year birds - sometimes over 50% and in one year actually wiping all the youngsters out. They also suggested that other mortality factors might include hunting on migration routes or the wintering grounds, the availability of Zostera or its local alternatives on the wintering grounds, egg and down collection on the breeding grounds, predation by carnivorous mammals (e.g. Arctic Foxes and Polar Bears on Svalbard) on the breeding grounds, or even competition from other, larger, geese such as Barnacle Geese for nest sites, etc.

Folkestone Harbour

A brief gull watch after the eco-poetry workshop.

I think this is a first-wintered plumaged Great Black-backed Gull, just moulted into its first winter plumage. It is likely to have moulted fairly recently, probably in October according to the books. The fairly clear chequered look is quite characteristic. The scapulars are quite fresh and with anchor-shaped patterns . The coverts are quite whitish overall, and therefore contrast with the darker secondaries beneath.  The primaries are quite well pointed, rather than rounded. The secondaries are relatively dark compared to later plumages. The bill is entirely black. The head is relatively pale, a fairly clear distinction from the juvenile.

This was the ringed young Great Black-backed Gull, which I have reported back to the Norwegian Ringing Group based in one of the southernmost peninsulas of the country. I am currently guessing that it is a second winter bird.

Here is an adult Great Black-backed Gull on the foul mud in the harbour.

This is I think a young Herring Gull, probably a first winter from the pointed tips to the primaries. The eye seems very high and far forward.

I saw a Common Guillemot in the outer harbour earlier on, and watched it "swimming downwards" as it dived.

A Long-tailed Duck was also reported, but I was in the middle of becoming a poet when it was supposedly seen opposite "Rock-Salt".

Reculver

Leysdown-on-Sea

A blowy day with quite a few others reporting birds like Pomarine Skuas flying past off the headlands of Kent.

Not quite so much in the brief time I was at Leysdown, but quite a few gannets way out to sea. On the shore some nice Herring Gulls.

This I think is a First Winter bird, as it has a dark eye, dark beak pretty much all the way to the tip, and rather pointy white tips to the primaries. However it might be a relatively immature Second Winter bird. It is possible that this bird is still growing some new outer primaries.

Stigmella aceris in the front garden

A nice mine to find, |Stigmella aceris on the Norway Maple of course. The only Stigmella known to occur on Norsway and Field Maple, there is a different species, Stigmella speciosa on Sycamore. The mine is filled with brown frass by this stage, my specimen does rather follow the vein a little more closely than in most photos on the web!

I could just about convince myself that I had found an egg at the start of the mine. The mine was paler at the far (expanded) end, perhaps where was less (or perhaps no) frass to fill the mine.

The larvae has been gone for many weeks of course - although I couldn't find an exit hole until I looked very carefully at the top surface of the leaf, where the final section of epidermis above the mine did appear to be missing.!

Oare Marshes thinking of Golden Plover again

The Golden Plover at Oare 

Eurasian Golden Plover, Pluvialis apricaria (Gravenhorst, 1820), (Desvignes, 1856). An interesting bird that seems to have declined in its UK breeding population steadily over the last few decades, perhaps due to changes including reductions in keepering on upland moorland, consequent increased carrion crow predation, reduction in moorland burning, possibly increased raptor numbers, or many other factors.

The much larger overwintering Golden Plover population from northern Europe, Russia and Iceland does also seem to have shifted its wintering distribution in the UK away from pastures in the West towards (particularly) arable land on the eastern side of the country since the 1980s. The Kent birds might seem to prefer grassland still but I well remember seeing birds on ploughed fields in Yorkshire on one journey up to see or pick up Simon.

In the early part of the winter in Kent, large numbers can be seen in the Swale and specifically at Oare Marshes. Today there must have been getting on for a thousand birds here at Oare today.  It is one of the twenty two sites listed in the non-breeding SPA for this species, each site being a multispecies SPA.

The plumages of the birds are quite variable in detail. This might be a juvenile or first winter bird on the left - underside more speckled further down the flanks and belly, and ONLY IN MY PERSONAL VIEW, a little warmer in the face and the supercilium thereby a bit less contrasty.

I checked for slender (long-legged?) birds with somewhat clearer supercilia and long wings projecting beyond their tails - but no possible American Golden Plovers as far as I could see!

The overall ecology of the bird is very interesting:

Moorland Breeding

In the small and declining UK population the birds nest on moorland, although during the incubation period the adults really like to feed on neighbouring farmland pastures on worms and cranefly larvae, etc, while their partners are incubating the eggs. During the day the males incubate and the females feed, and during the night the females incubate and the males feed. Tipulids are a key feature of both the later adult and the chick diet. Pearce-Higgins and Yalden showed in one of their South Pennines studies (2003) that the particular arable, improved and pasture fields chosen by the off-duty birds for foraging in were those with appropriate pasture sward heights, appropriate moisture levels and good numbers of earthworms and particularly cranefly (Tipulid) larvae. Over time, sheep stocking density has increased in UK uplands, which might be helpful, but is also associated with agricultural intensification such as drainage, which would probably reduce Tipulid numbers.

According to Whittingham et al., working on moorland in Northern England in 2001, chicks on the moorland tend to use mosaics of dwarf shrubs such as willow, crowberry and bilberry, and more open areas of cotton-grass and bare peat. Again Tipulids and Beetle larvae do tend to be very important in the diet. Rotational strip-burning or careful manipulation of grazing management systems could be used to help maintain these mosaics.

Later in 2011 Pearce-Higgins did some very interesting theoretical modelling on the extent of the impact of expected climate change on this population on the southern edge of its range, and suggested that the impacts would greatly reduce Tipulid numbers, and chick survivability, and proposed equivalent increased management activity to help maintain the population, either environmental management to increase Tipulid food sources by 80%, or by reducing nest and egg predation by 35%.

There are birds in Sweden that also breed in the uplands, like the UK breeding population, although the habitat there is referred to as Fennoscandian arctic tundra. Machin et al in 2017 showed that the chicks in this habitat in Sweden feed on a more diverse diet of beetle larvae, cranefly larvae and St Marks Fly (Bibionids) larvae, and breeding success appears to be at least in part linked to Bibionid population fluctuations from year to year. The Bibionids are found more in willow scrub, and the chicks may move into this habitat as they grow in part according to prey availability, but also in part in order to gain increased protection from predator attack.

Over-wintering

After the young have fledged, the adults and young migrate to lowland farmland and coastal habitats for the autumn and the winter. According to Gillings et al., in 2007, in recent decades winter populations of both Golden Plover and Lapwings appear to have switched from using pastures in the west of the country to using arable land for much of the winter - October - February (harrowed fields for winter cereal initially, then sugar beet and then other crops). Large open fields which had been manured were particularly favoured, and it is perhaps to be hoped that both manuring and sugar beet growing will continue into the future for these large numbers of birds over-wintering in the UK. However the reasons underlying the move and whether the pastures have become less attractive, or the arable more attractive, or both or neither remains a bit of a mystery. Could climate change have impacted on the relative attractiveness of these two types of habitats? In France research reported in 2007 indicated that cereal fields were the preferred wintering habitat in that country.

As for field size, Leitão and Peris working in Portugal in the late 90s concluded that Golden Plovers avoided fields less than 10 Ha, and preferred fields larger than 20 Ha, and preferred pastures in this particular environment.

Birds migrating from further North and East in Europe and Russia use arable fields in southern Sweden as autumn staging posts, where Lindstrm et al. showed in 2010 that numbers tend to be quite high and they are able to both moult and then also (critically) put on weight after their moult for the next stages of their journey, perhaps to the UK. The adults and young follow more or less the same pattern although the young do follow the adults after a little delay. The length of stay on these fields is about three months, August to November, indicating the importance of this habitat to this population of migrating birds.

Research reported by Piersma et al in 2003 into birds over-wintering in the Netherlands showed some fascinating patterns. The birds put on weight in the autumn (September - November) and their weights peak in late November and December as they (presumably) put on fat to sustain themselves in bad times. They then lose weight again - I imagine as they use up their reserves, perhaps with somewhat poorer food availability. Then in the spring they start to put on weight again, perhaps as food becomes more available again, in preparation for their spring migration and the breeding season to come.

However between the 80s and 90s, the December peak mass decreased as the weight gain stopped earlier, although the rate of increase during the shorter period of weight gain remained the same. As weather conditions remained similar, this was interpreted as a response to increased raptor numbers, such as Peregrines and Goshawks - possibly leading to slimmer fitter birds more adapted to raptor evasion. However this seems to me to be a rather over-optimistic view of the ability of these birds to plan ahead, and to control their weight!

Machin et al reported in 2015 on individual winter movements of birds from a breeding population in Swedish Lapland, showing that some started their winters in NW Europe in areas such as northern France, and shifted south to Spain or Africa in cold spells, giving a degree of flexibility to their over-wintering, while others sometimes didn't move further and stuck out the cold spells where they were. Cold weather movements were noticeably long and fast, real escape movements.