Trip reports

Normandy & Pennington Marshes

Normandy & Pennington Marshes
Bar-tailed godwit in winter plumage by Ian Kirk on Wikimedia

Friday, 12 November 2021

Fourteen members of the local group enjoyed a circular walk along the sea wall and back inland to the car park in windy but mild conditions. In total we saw 66 species that included a good cross-section of wintering waders and wildfowl.

Two birds of particular interest, which are rare over-wintering waders on the south coast, are the ruff and the bar-tailed godwit. Most ruffs spend the winter in Africa, although some males are inclined to stay nearer to their breeding territories in northern Europe. Breeding male birds sport ruffs and ear tufts in a variety of plain or barred combinations of rufous, ginger, white and black. They display on the ground in leks with dominant independent males establishing a small territory that is visited by females for mating only. These dominant males have a combination of dark ruffs and ear tufts and show a varying degree of tolerance to what are known as satellite males that are predominately white in colouration. Satellite males can mate with females whilst the dominant male is distracted or loses control of his attendant females. It has been demonstrated that having a satellite male enables the dominant bird to mate with more partners. There has been evidence to suggest that white-plumaged birds have lower levels of testosterone than dominant males which accounts for their submissive attitude when they are occasionally attacked by them. This is just a short insight into their complex breeding behaviour. The bird that we saw was a satellite male, despite being in winter plumage it was completely white apart from its wings. You would have thought that a white bird would have been particularly prone to predation, especially as peregrines hunt on the marsh. On its breeding territory satellite birds pay a good deal of attention to the behaviour of other ruffs and consequently it is no more likely to be predated that any other bird. Our bird was associating constantly with a large flock of starlings; therefore, I would surmise it was using them as an early warning system.

We saw about 10 bar-tailed godwits; normally you would be fortunate to see one or two. These birds breed from Norway right across to Alaska and winter mainly from West Africa to New Zealand. They hold the endurance record for any migrating bird, flying 6,000 miles from Alaska to New Zealand non-stop in a journey that takes about a week. They show a remarkable physiological adaptation that enables them to undertake this flight. A bar-tailed godwit was once found dead having struck a radio tower as it was setting out on migration from Alaska. Its fat deposits accounted for 55% of its weight It also had an enlarged heart and breast muscles but had absorbed most of its digestive tract (meaning that it could not feed), and had reduced the size of its gizzard, kidneys, and liver. By reducing the size of these organs, it was carrying less weight thereby saving energy. The godwits regrow these organs on arrival on their wintering grounds and can soon recommence feeding. This strategy is used by a number of long-distance migrants, particularly in waders and wildfowl, but this is the most extreme example.

Reported by Mark Barrett

Species List: mute swan, Canada goose, brent goose, wigeon, teal, shelduck, pintail, mallard, gadwall, shoveler, tufted duck, red-breasted merganser, pheasant, great crested grebe, little grebe, little egret, grey heron, peregrine, kestrel, moorhen, coot, oystercatcher, redshank, black-headed gull, dunlin, curlew, turnstone, black-tailed godwit, bar-tailed godwit, ruff, snipe, knot, ringed plover, lapwing, grey plover, greenshank, spotted redshank, herring gull, black-headed gull, great black-backed gull, lesser black-backed gull, wood pigeon, green woodpecker, skylark, meadow pipit, pied wagtail, dunnock, robin, stonechat, blackbird, Cetti's warbler, wren, great tit, blue tit, long-tailed tit, jay, rook, carrion crow, magpie, starling, house sparrow, goldfinch, chaffinch, greenfinch, linnet, reed bunting

References:
Johan G Van Rhijn, The Ruff, T and AD Poyser, London, 1991
Ian Newton, Bird Migration, New Naturalist, Collins, London, 2010