Exotic Gulls at RSPB Dungeness

Well, perhaps not that exotic, but very interesting to finally see these two relatives of Herring Gulls from warmer climates!

This is a Yellow-legged Gull, Larus michahellis, from Southern Europe, the Mediterranean and North Africa, which was on the board as present and visible from the Scott Hide, but I am still glad to say that I did find it without it being pointed out to me, or knowing that it was still there.

Here is a reasonable picture of the bird, but a little blurry due to camera shake - the light had gone down much faster than I imagined, and I lost exposure speed in comparison to the fixed ISO and aperture. I spotted the very white head and yellow legs fairly quickly when I first saw the bird, but there are other features that I think can be picked out, according to the books and websites. The back and mantle are a trifle darker grey than the normal blue grey of the Herring Gull, although this can often be a little misleading, even minute to minute as birds turn from one angle to another, or the light changes.

Looking at the photo, it does look quite a "neat" bird, full-chested, perhaps slightly leaning forward, with a long "fuscus"-like rear end. The legs do look quite long, and the bill looks quite large and parallel-sided. It is certainly quite a bright bill, with an extensive red gonys-spot. The eye is quite small and beady at this distance, which was out in the middle islands on Burrowes Pit.

Black-necked Grebe at Dungeness

Dungeness

Got onto the reserve at about 3 pm, and had a look at the birdfood before I went off to the Frith Hide. There were good views of the large gulls, mainly Herring, but also Lesser and Great Black-backed Gulls. The juveniles were particularly intriguing. The sub-adult Lesser had a good black stripe at the tip of the bill. The young Great Black-backed was particularly scaly.

From the Scott hide, different views of the Gulls, and many Cormorants. One Cetti's warbler close to the hide.

Back to Dennis' hide, and very good views of the drake and two duck Smew, Mergellus albellus, together with the related Goldeneye, here two drakes and three duck, all in one telescope view.

Why are there so many more female Smew than there are males? Even in German winter quarters, there are only 45% males, and in Britain females greatly outnumber males. The answer is given in a Birdworld article: "and as if to rub in their sparing patronage, Smews don’t even send us many of their best. Although the females, and the similarly plumaged first-winter immatures, are distinctive and dapper birds, they cannot compete for sheer looks with the males. A true Smew is a male Smew, with its authentically snow-tinged plumage and smart black blobs and lines that break up its outline. Yet we receive many fewer of these than females and immatures. The reason is a phenomenon known as differential migration. In many species of birds, different age classes of birds have different migratory profiles. Most typically, adult males undertake the shortest journeys, staying as close as possible to the breeding grounds so that, when the time comes, they can sprint quickly to occupy their high latitude territories. Females also tend to be smaller-bodied than males, and potentially suffer in competition with them, so they migrate longer distances, keeping them away from the males and allowing them to nestle in more gentle climates. But the result of this differential migration is that we, at the far end of the Smew’s migration, are starved of seeing the handsome males. The migration is differential, and also discriminatory." Generally when in England they are traditionally found South of the Wash (this may be less true nowadays), and may be temporarily driven over from Holland in severe episodes of winter weather.

The Smew, Mergellus albellus, is one of the smallest members of the sawbill group of duck. Like the other Mergansers in the main genus Mergus, and also in the tribe Merginae, the bill is serrated. In the winter and early spring, the Smew's diet is mainly fish, either on salt or fresh water. On the breeding grounds, when the birds move from the rivers to the lakes as they unfreeze, the diet changes to insects. In November, when the insects die or drop to the bottom of the lakes, the diet changes abruptly back to fish.

The female is most easily recognised at distance by its flattened shape, and the obvious white cheeks. Next the red cap is fairly easily picked out, against the generally light grey bird. The narrow white wing bar can be seen at rest, and can be seen as one of the three white sides of a square when the wing is extended - or that's what it looked like to me.

The male is obviously primarily white, with black lines and greyer areas on the flank. The shape is again quite distinctive, particularly the steep forehead. The bill is particularly delicate.

On the breeding grounds the birds use dead trees, often holed by Black Woodpeckers for nest-sites. They readily adapt to nest-boxes. Threats to the population include habitat loss particularly affecting nest-sites such as logging and river canalisation, oil pollution, and hunting while on passage.

Slavonian Grebe at Dungeness

Wandered down to Dungeness in the late afternoon, largely to have an afternoon away from the house.

At the Visitors' Centre the kind volunteer lady let me in without my membership card, on my word alone. What very nice people in the RSPB.

I went to have a brief look at the feeders, but there were only some very tidy Great Tits there, no Tree Sparrows that I could see! I then went over to Dennis' hide where there were plenty of Tufted Duck and Pochard in front of the hide, with some Coot, Shoveller and one Great Crested Grebe as well. There were Great Black-backed and Herring Gulls off to the right. At the back in the distance and to the left was the Slavonian Grebe, nice and tidy!

I could see the white breast and cheek, with the red eye very obvious when struck by the light. It was similar to a Little Grebe, but with a tidy shape, with the rear less fluffed up, a slightly greyish lower side, and a very clear demarcation between the black of the cap and the white of the cheek. The head shape was relatively flat, with the beak reasonably level, so not quite as would be expected from a Black-necked Grebe, which has a "peaked cap" above the eye.

Importantly I couldn't see any brown on the bird, so rather unlike most views of the Little Grebe in winter, and thus the monochrome colouring suggesting Slavonian, Black-necked or Red-necked Grebe. The features I didn't really see were the narrowness of the rear neck-stripe as seen from the rear, and the patterning of the smudging on the neck.

At one point all the duck just underneath the hide windows took off as one, and then a lady in the hide pointed out the female-type Marsh Harrier on the other side of Burrowes Pit, which steadily flew left to the right over the far shore.

The grebe swam about quite actively, then had a dive, starting with a very small jump (Helm has it as "tends to spring forward with a quick dapper action", and when I left it was "asleep", resting its head and beak on its back, in amongst a small raft of Tufted Duck.  A lovely bird, even in its somewhat monochrome winter plumage!

I went over to the ARC pits, but saw little more apart from more Coots and Gulls, although as I was leaving I thought I saw a Raven fly over the track.

The winter plumage description states that the cap is glossy black while the back of the neck is really actually a dark grey, as opposed to black, and it may be broken up with pale feathers. The cheek,sides of nape, foreneck and breast obviously white. Flanks a mottled dusky colour, and the back should be a matt black.

The habitat is said to be a bit more northerly than other species, properly holearctic boreal in fact. Generally prefers eutrophic well vegetated waters, but can be found on quite oligotrophic "naked" waters in Iceland for example. Can be at higher altitude than the other species, but rarely higher than 300 m. Prefers depths of water generally 2.5 m or less, with submerged vegetation. If nesting on very small ponds, may fly to feed on larger water bodies. It flies quite readily. Tolerates quite close human presence. It first bred in Scotland in 1908 and has increased slowly since then. The Scottish Lochs are generally occupied from March to September, failed breeders leaving first.

Overwinters either inshore on the coast or sometimes large lowland lakes. The (large-billed form) Scottish birds probably winter in the North Sea or the Atlantic Coast of Ireland. The birds in the Southeast appear to be the (small-billed form) birds from Northern Europe eastwards from Sweden across northern Russia.

Food chiefly arthropods (such as insects and larvae) and small fish, occasionally crustacea, mollusca, annelids and plant material, obtained mainly by diving with the average dive lasting about 30 seconds, depending on density of prey. Feathers generally also eaten. Can also feed on surface. Feeds mainly by daylight, usually solitary.  

Monogamous pair-bond for the season, generally initiated on migration or in winter quarters, so most paired on arrival. Various posture displays and dances. Nest well hidden, spread out as breeding pairs are quite territorial. Often floating but anchored to the substrate. Usually one pair per small pool, or per bay of a large lake. Both parents incubate, eggs covered with down if sitting parent disturbed. Hatching asynchronous, egg-shell removed. Usually one brood, occasionally two. Young carried on back of parents after second day. Fledging period 55 - 60 days. Young become independent at 45 days or less. After departure of the parents, the siblings and perhaps other young may form small groups. Outside the season generally found as singles, or pairs or small groups on the wintering grounds. Age of maturity probably two.

Dungeness with ducks, grebes and geese.

I was very pleased to see a female Goldeneye on the left viewing from the Dennis hide, and then delighted to see a small group flying across the front to the right in front of the old lighthouse, which I just managed to catch with the Sigma lens.

I talked a bit about the male displays and the overall lifestyle in another blog, Goldeneye at Cliffe Pools.

It was really nice to see the Great Crested Grebes fairly close in to the front of the hide:

There were good numbers of Northern Shovellers, Anas clypeata, all across the Burrowes Pit. In this individual the whitish channel of feathers between the chestnut ones above the leg can be seen. I have looked for it online, and detected it in a number of other examples, where the thighs are thrust forward. However I have to say that I don't understand exactly what is going on here. Could it be the down feathers beneath?

A closer view:

A view of the white channels from the rear! You can also see the tail pattern of the central dark area with the surrounding white feathers to the side of the tail.

There are four species of Shoveller ducks in the World, the Northern, Anas clypeata, that we are familiar, the Cape, Anas smithii, from (mainly) Southern Africa, the Australasian, Anas rhynchotis, from Australasia (!), and the Red, Anas platalea, from South America. They are all in the genus Anas, and I assume that they all have a common origin - perhaps!

The shape of the bill is to do with the feeding diet. The bill is used to filter tiny animals such as Cladocerans, such as Daphnia, and Ostracods out of the water. This is a very specialised diet, and one of the major problems is that Cladoceran populations crash in mid-summer, leading to significant weight loss over the summer in the Shoveller males, and even apparently death in the females, and perhaps the young, despite their attempts to turn to alternative sources of food. The males cope at least in part by really great efforts to build up reserves by intensive foraging earlier in the year, and then minimising their foraging when their diet is scarce, apparently remaining in hiding, somewhat unseen.