This is really quite a strange time of year as we get to a whisker away from the shortest day, the 21st December - a particularly emotional time for me as it was my father's birthday. There are both lingering elements of the season drawing to a close, and signs of the new season to come, all mixed in with the feeling of the depths of winter and the excitement of the wintering flocks of birds visiting us, seeking refuge from the icy North.
On the gravel pits the duck are thrilling, with Shoveller numbers starting to build a little bit more strongly now, Teal, and the fantastic female Goosanders (there are now THREE of them, all red-heads), all adding to the semi-resident Gadwall, Mallard and Tufted Duck. I'm still hoping for another Smew this winter, to match last year's cracker! Its difficult to get good photos of the duck at distance, so instead here is a shot of the black-headed gull roost in the second gravel pit, which is always worth a careful check!
Here are some of the group of gulls on the wooden perches to the South of the second gravel pit, and as usual this is a good place to look for Common Gulls,
Larus canus. There are 3 in this picture, and these are numbers 4, 7 and 8 counting from the left in this group of 9, the others being the much commoner black-headed gulls! It may be possible to pick out the Common Gulls by their somewhat larger size, and their yellowy-green legs and bills. They are very much inshore gulls, nesting on freshwater lakes and gravel pits, and feeding on the shore and inland. They breed in colonies to which they return in successive generations (monogamous pairs persist year by year), with nearby pairs being more highly related to each other, and a surprising degree of neighbour adoption of wandering chicks. The Birdtrack records indicate numbers in this tetrad between 1 and 4 during 2010, but surprisingly there are no records shown there for 2011.
These three all look like adults, with no obvious black on the bills, although this is very easy to miss - as adults they should have thin black lines on their bills in winter, but no large black patches at the base. They could have migrated into this area for the winter, or they could be part of the resident population in the Southeast. If they have migrated here, they could be from Scandinavia or from Scotland. The total UK population is estimated to be about 50,000 birds, and all those mainly Scottish birds must go somewhere in the winter! Birds are quite subject to predation and do contain quite a diversity of helminthitic parasites, few dominant core species, like other gulls. Males take 2 - 3 years, females 3 - 4 years to start breeding.
Perhaps also they are part of a larger group that roosts here at night, and the others all move off as a flock to feed as a Common Gull group? This seems unlikely as the Common Gulls that Warren usually sees are generally mixed in with the Black-headed Gulls, and there probably aren't enough Common Gulls to make a flock of their own. It's very difficult to get to understand questions like these. Now that I have my eye in a bit, I generally see 2 or 3 birds here during the day, but I've no idea if they are usually the same birds each time, nor whether they are accompanying the Black-headed Gulls or operating independently, for at least part of the time!
Many gull species have increased their populations significantly in the twentieth century, taking advantage of new opportunities at sea and on land, following fishing boats, frequenting waste tips, following the plough, etc. Research in Germany near the Baltic indicated that the Common Gulls there preferred quieter pastures to feed on in flocks, separating their niche from the Black-headed Gulls, which were much more likely to be following the plough on disturbed arable fields. However 20% (!) of gulls following tractors in this study were still Common Gulls, although they spent more time than the BHGs foraging outside the flock, the BHGs tending to follow the tractors more closely.
The German research took seasonality into account, and counted the gulls in different fields, estimating their behaviour patterns. The arable fields in general were available as bare earth being cultivated during migration periods and the winter, but tended to have over-tall vegetation for exploitation during the summer breeding season. The Black-headed Gull numbers fluctuated by season, while the Common Gull numbers were steadier, although both species are migratory.
I wasn't very happy with the statistical approach adopted in this paper, and I think it may have obscured some of the real issues. In addition we don't know where the gulls were when they weren't on the fields, and what they were feeding on as alternate sources! They could be on waste tips, or on the intertidal flats, feeding perhaps on bivalves and polychaetes. Its also worth remembering that there is a lot of flexibility and variation between sites and years in these highly opportunistic birds!
However, according to this research, the Common Gulls spent most of their time foraging in their pastures feeding on earthworms, particularly during autumn and early winter when earthworm biomass is highest, and didn't rest as much as other species. The Black-headed Gulls fed on insects disturbed by the plough, and also spent a little time trying to catch flying insects. They feed hugely at these temporarily abundant resources, and then spend more time resting than the Common Gulls tend to. The BHGs I see by East Lock generally seem to be trying to scavenge things off the ground, either on the newly sown cereal searching from the air, or from the sheep pasture searching on the ground - mostly I don't see Common Gulls on the local farmland at all!
The intensification of arable operations should benefit BHGs, while the move from grassland to arable across Europe may negatively affect Common Gull numbers, particularly as livestock is now more supported by forage and silage, as opposed to traditional pasture grazing, which provides the undisturbed insect and earthworm-rich resources that Common Gulls seem to like.
Back to the blog, this is the causeway across the second lagoon, with great views of the Common Reed fringing the gravel pits,
This is one of the little islands in the shallow lagoon in the first pit, that Monty likes to check for nesting duck if he escapes control - I have to make sure he never does that again.
There are still fruit on the bushes to tempt the visiting winter thrushes, and this is a close-up of two rose hips - the third has already been taken, perhaps by a Fieldfare or Redwing!
The hedgerow roses often seem to have small sections where the leaves remain green and apparently functional, and I've no idea if this is simply an error by the plant, or whether it manages to get a bit more photosynthesis done by developing this little trick! Blackberries seem to retain at least some green leaves for ages.
The rose thorns are retained as well of course, those that haven't got picked up in Monty's coat as he drags through the hedgerows looking for rabbits and squirrels!
By the side of the path to the East of the first gravel pit, there are a number of Goat Willows
On the Goat Willows the buds seem to be swelling - a sign perhaps of the pussy willows to come - if so its got to be a portent of spring hoverflies to come I hope!
This particularly well coloured twig might be a
Cornus I suppose?
Meanwhile the lichens continue slowly and steadily to make the most of things by colonising the bark of the oak trees, growing quietly whatever the season! These mainly crustose ones are on the vertical trunk near ground level, greatly magnified,
While these frondose ones are on the stub of a horizontal branch, broken off and rotting further along at the tip
Approaching the lock across the sheep pasture on the return journey, the alder was in its full red-headed glory with its catkins coloured up and getting ready to shed their pollen, another promise of the spring to come. As with so many alders the tree itself leans - I wonder why this is a specific characteristic in so many trees?
Just on the North side of the Lock, I found a blue tit excitedly exploring a dead or dying branch, trying to rip bits of peeling bark off, presumably looking for insects. I got a few shots despite the distance, the blocking branch and the shadows - apologies for the poor quality!.
Looking downriver, the sheep were accompanied by black-headed gulls on the meadow. I could only see a few in this view framed by the bank-side vegetation, but the framing looked rather good!
Just above the lock a big bale of straw had got dropped into the river, by accident or design, and could become a minor hazard to shipping!
On the walk back across the fields, there were some heads of the Common Hogweed,
Heracleum sphondylium, and this one has just caught the light on its dried capsellas, just asking to be sown ready for next season!
In the hedgerow wind-break above the hogweed, the Fieldfares and Starlings were prominent in the bare branches and chatting to each other loudly.
Bird count seen at or from the pits themselves: 1 Canada Goose,
Branta canadensis, 5 Teal
Anas crecca, 57+ Gadwall,
Anas strepera, 26+ Tufted Duck,
Aythya fuligula, 11+ Mallard,
Anas platyrynchos, 15 Shoveller,
Anas clypeata, 3 Goosander,
Mergus merganser, 3 Great Crested Grebe,
Podiceps cristatus, 8 Little Grebe,
Tachybaptus ruficollis, 140+ Lapwing,
Vanellus vanellus, 3 Common Gull,
Larus canus, 3 Mute Swans,
Cygnus olor, 110+ Black-Headed Gulls,
Chroicocephalus ridibundus, 1 Herring Gull,
Larus argentatus, 110+ Coot,
Fulica atra, 1 Moorhen,
Gallinula chloropus, 3 Grey Heron,
Ardea cinerea, 9 Cormorant,
Phalacrocorax carbo, 2 Jackdaws,
Corvus monedula, 1 Magpie,
Pica pica.
In the field at the bottom of Kelchers there were 9 Fieldfare, 7 starling, 5 blue tit, 5 Long-tailed Tit, 4 blackbird, 2 wren, 3 Goldfinch, 5 chaffinch, 7 woodpigeon
