8 Nov 2008

7th November 1988 - the Brouwersdam

The six kilometre long Brouwersdam separates the Grevelingenmeer from the North Sea. It carries one major and two minor roads and has plenty of parking space facing the sea. We drive slowly along the now-deserted parking area and stop after about 500 metres to look at the gulls roosting there at high tide. Thick fog preventsd us seeing anything on the water.

They are almost all herring gulls and we have ample opportunity to study adult and immature winter plumages. With all types together the different ages are obvious ‑ quite brown for those still in juvenile plumage; much paler heads and bodies for those moulting into first winter; grey mantles and scapulars with brown still in the coverts for second winter. Third winter birds look like adults on the ground but in flight they show more extensive black tips to their wings.

A few turnstone and a purple sandpiper run in between the gulls, picking up small items; and large numbers of oystercatchers roost further along.

The fog suddenly lifts and birds became visible up to 400 metres out on the sea. There are several great-crested and about a half dozen red-necked grebes. This is the first time we have seen the two species close together and the difference in shape is quite marked; the red-necked look more like overgrown little grebe with an extra large, yellow‑based bill. Two of them have a brief encounter of the aggressive kind, growling and wing-flap­ping, and showing clearly their double white wing‑patches.

A small group of eider float close to the shore. Eider first breed at three to four years and males show a great variety of plumage before attaining adulthood. Amongst this group are several variations, including one with white speckling on the mantle and scapulars, probably a first winter, while another has a rather dirty looking version of adult plumage. The more plain brown birds had an indistinct buff super­cilium, indicating juvenile plumage, and of these some had dark backs suggesting males.

The birds start feeding, diving directly from the surface and opening the wings as they were half way under. Food, mainly mussels and crabs, is often swallowed underwater, but some­times a bird comes up with a bunch of mussels which it seems to turn and crunch a few times before swallowing.
The tide is going out and exposing a sandy shore. In places the sand has been blown in to form quite large dunes, some of which have been stabilised with marram grass and thistles while others are being fixed with brushwood to prevent them blowing over the road. It is hoped that these dunes would become nature reserves for breeding birds.

A small wader hurries along the beach like a clockwork mouse, obviously a sanderling. In fact, there are several at intervals along the shore; they seem to have established feed­ing terri­tories for there is often calling and chasing when two birds met on their invisible boundaries.

In the same area there are the remains of four large fish on the beach ‑ whole heads with backbone and tail still attached. The first of these is being eagerly attacked by an immature great black‑back gull, the next by a second winter herring gull. The black‑back abandons his prize in favour of that held by the herring gull who in turn goes across to attack the first fish. The third fish is the possession of an oystercatcher while the fourth is commandeered from an adult herring gull by another immature great black­back. The herring gull, and a mate, stand by to await their next opportunity.

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