Key Bird Species on the Thames Estuary
The tidal Thames provides habitat to a wide range of important bird species, particularly overwintering and migratory birds. Many of these species are listed on Annex I of the Birds Directive.
The Avocet (Recurvirostra avosetta) is an Annex 1 species and is present in internationally important numbers on the Thames Estuary and Marshes SPA. The species is restricted to the lower marine reaches of the river. The mudflats at Higham Bight and Mucking Flats are particularly important for this species and small numbers also breed amongst the saline lagoons at Cliffe. The species can be identified by its black and white plumage and characteristic long up-curved beaks. Avocets feed on insects, crustaceans and occasionally small fish.
Black-tailed godwits (Limosa limosa) prefer muddy estuaries, where they feed on intertidal invertebrates, including molluscs, ragworms, crustaceans and earthworms, locating their food by sight and touch. Their plumage changes between winter and summer, with their chests turning a bright orange-brown colour in the warmer months and their plumage becoming grey-brown overwinter. Their most characteristic features are their long beaks and legs, and the black and white stripes on their wings.
Dark-bellied brent goose
The dark-bellied brent goose (Branta bernicla) winters in Britain in internationally important numbers. It breeds in western Siberia and winters in Western Europe, with about half the population in Britain. The species feeds on eelgrass and green algae which grow on mudflats. Once these food sources are depleted, the birds move inland to feed on coastal arable farmland and pasture. The birds roost on sheltered coastal and estuarine waters and can be identified by its black head and neck, grey-brown back and dark belly.
Dunlin (Calidris alpina) feed in extensive muddy areas of estuaries on a wide range of invertebrate prey, including polychaete worms, gastropod snails, bivalves, crustaceans and occasionally small fish. They are the second most widespread wintering estuarine species in the UK. They are the most numerous species on the Thames Estuary and Marshes SPA. As over-wintering birds on the River Thames, they can be identified by their winter plumage of white, grey and black and black slightly downturned beak and black legs.
European white-fronted goose
The European white-fronted goose winters in Britain in nationally important numbers. It breeds in western Siberia and winters in Western Europe, with about half the population in Britain. It overwinters in nationally important numbers on the Thames Estuary and Marshes SPA. White-fronted geese forage on farmland for grass, clover, grain and winter wheat. The number of European white-fronted geese over-wintering on the Thames Estuary SPA has decreased sufficiently to trigger a long-term Medium alert. The magnitude of the decline is, however, influenced by uncharacteristically high counts in the late 1960s, since when, numbers have decreased, but not as rapidly as suggested by the alert. The trend contrasts with that of the region, which has fluctuated but generally increased, but is in line with the national trend, with little evidence of a decrease in the proportion of the national WeBS total hosted by this site. Combinations of factors are thus responsible for triggering this alert (Maclean et al., 2005).
The gadwall winters in Britain in internationally and nationally important numbers, predominantly on inshore waters (Batten et al., 1990). The Greater Thames Estuary Natural Area supports at least 5% of the wintering British population (English Nature, 1997). The Lee Valley and Southwest London Waterbodies SPAs, (approximately 20kms upstream from the current study site) are designated for their high numbers of wintering gadwall. Within the study area the species occurs in nationally important numbers at Cliffe Pools. No WeBS alerts have been triggered for this species.
This species is widespread in the Thames Estuary. Their diet comprises polychaete worms, molluscs and crustaceans. Overwintering in the River Thames, the grey plover (Pluvialis squatarola) can be identified by its grey-brown feathers and characteristic black armpits as it flies.
This is the third most numerous estuarine British wader, with an average population of 220,000, the mudflats of the Thames estuary are important wintering sites for this species. Knots (Calidris canutus) are specialist feeders on marine bivalves and is similar in appearance to the dunlin (C. alpina) but with orange-brown legs instead of black.
Lapwing (Vanellus vanellus) are the most numerous estuarine British wader; they forage on saltmarsh for a variety of invertebrates. Within the Thames Estuary there is widespread suitable habitat for lapwing in the lower Thames Estuary. Lapwing can be identified by its black and white feathers, rounded wing shape and crest on top of its head.
Little grebe (Tachybaptus ruficollis) chiefly overwinter on inland freshwater sites, approximately 10% overwinter on estuaries and coastal habitats and the Thames estuary is an important wintering site. In summer, this species has a characteristic bright chestnut throat and cheeks with a pale gape patch at the bottom of the bill.
Wintering oystercatchers (Haematopus ostralegus) are associated with sandy estuaries and cockle and mussel beds. They are widespread throughout Britain with the Thames Estuary supporting at least five per cent of the wintering British population. Oystercatchers are black and white birds with a long orange-red bill and red-pink legs.
The Icelandic population of pintail spends the winter in Britain, favouring coastal marshes and estuaries, flooded grassland, lakes and reservoirs. They eat a variety of plants and invertebrates. The Greater Thames Estuary Natural Area supports at least 5 per cent of the wintering British population (English Nature, 1997). Within the study site, Cliffe Pools supports nationally important numbers of pintail (RSPB). A positive WeBS alert has been triggered for this species on the Thames Estuary and Marshes SPA due to high increases in numbers over the long-term.(Maclean et al., 2005).
Redshank (Tringa totanus) overwinter in nationally important numbers on the saltmarshes of the Thames Estuary. Small numbers also breed on the wetter grazing marsh areas adjacent to the Thames in the lower reaches of the estuary. They are known to feed on a variety of invertebrates, including crustaceans, molluscs and polychaete worms. Redshank can be identified by their characteristic orange-red legs, brown speckled back and wings with an orange base to their beak.
Ringed plover (Charadrius hiaticula) are widely distributed along the lower reaches of the river in numbers of international importance. The Thames Estuary and Marshes SPA and Benfleet and Southend Marshes SPA represent nearly three per cent of the UK's passage population of ringed plover. They feed on invertebrates in a variety of intertidal habitats and roost communally, close to feeding sites along the shoreline, on sandbanks or bare arable fields and in low vegetation. This species has an orange bill with a black tip, orange legs and a black and white pattern on its head and breast.
Shelduck (Tadorna tadorna) has a coastal distribution in Britain, with intertidal sands and mudflats forming its main foraging areas, it feeds on a variety of invertebrates. Breeding shelduck are widely distributed within the tidal Thames. The Thames Estuary and Marshes SPA supports significant numbers of wintering shelduck. This species has a dark green head and neck with a chestnut stripe across its chest and a red bill.
Shovelers (Anas clypeata) winters in Britain on shallow freshwater areas with plentiful marginal reeds or emergent vegetation. The UK is home to more than 20 percent of the north western European population. They feed on small insects and plant matter and the males and females differ in appearance. Males have dark green reds, white breasts and a chestnut flank whilst females are mottled brown in colour.
Page updated 15/2/2022