Wader in the context of Dotterel

A water bird, alternatively waterbird or aquatic bird, is a bird that lives on or around water. In some definitions, the term water bird is especially applied to birds in freshwater ecosystems, although others make no distinction from seabirds that inhabit marine environments. Some water birds (e.g. wading birds) are more terrestrial while others (e.g. waterfowls) are more aquatic, and their adaptations will vary depending on their environment. These adaptations include webbed feet, beaks, and legs adapted to feed in the water, and the ability to dive from the surface or the air to catch prey in water.

The term aquatic bird is sometimes also used in this context. A related term that has a narrower meaning is waterfowl. Some piscivorous birds of prey, such as ospreys, sea eagles, fish eagles, fish owls, and fishing owls, hunt aquatic prey but do not stay in water for long and live predominantly over dry land, and are not considered water birds. The term waterbird is also used in the context of conservation to refer to any birds that inhabit or depend on bodies of water or wetland areas. Examples of this use include the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the Wallnau Waterbird Reserve.

Port Phillip (Kulin: Narm-Narm) or Port Phillip Bay is a horsehead-shaped enclosed bay on the central coast of southern Victoria, Australia. The bay opens into the Bass Strait via a short, narrow channel known as The Rip, and is completely surrounded by localities of Victoria's two largest cities — metropolitan Greater Melbourne in the bay's main eastern portion north of the Mornington Peninsula, and the city of Greater Geelong in the much smaller western portion (known as the Corio Bay) north of the Bellarine Peninsula. Geographically, the bay covers 1,930 km (750 sq mi) and the shore stretches roughly 264 km (164 mi), with the volume of water around 25 km (6.0 cu mi). Most of the bay is navigable, although it is extremely shallow for its size — the deepest portion is only 24 m (79 ft) and half the bay is shallower than 8 m (26 ft). Its waters and coast are home to seals, whales, dolphins, corals and many kinds of seabirds and migratory waders.

Before European settlement, the area around Port Phillip was divided between the territories of the Wathaurong (west), Wurundjeri (north) and Boonwurrung (south and east) people, all part of the indigeous Kulin nation. The first Europeans to enter the bay were the crews of HMS Lady Nelson, commanded by John Murray and, ten weeks later, HMS Investigator commanded by Matthew Flinders, in 1802. Subsequent expeditions into the bay took place in 1803 to establish the first settlement in Victoria, near Sorrento, but was abandoned in 1804. Thirty years later, settlers from Tasmania returned to establish Melbourne (now Victoria's capital city) at the mouth of the Yarra River in 1835, and Geelong at Corio Bay in 1838. Today, Port Phillip is the most densely populated catchment in Australia with an estimated 5.5 million people living around the bay; Melbourne's suburbs extend around much of the northern and eastern shorelines, and the city of Geelong sprawls around Corio Bay in the bay's western arm.

The webbed foot is a specialized limb with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved many times across vertebrate taxa.

It likely arose from mutations in developmental genes that normally cause tissue between the digits to apoptose. These mutations were beneficial to many semiaquatic animals because the increased surface area from the webbing allowed for more swimming propulsion and swimming efficiency, especially in surface swimmers. The webbed foot also has enabled other novel behaviors like escape responses and mating behaviors. A webbed foot may also be called a paddle to contrast it from a more hydrofoil-like flipper.

The ruff (Calidris pugnax) is a medium-sized wading bird that breeds in marshes and wet meadows across northern Eurasia. This highly gregarious sandpiper is migratory and sometimes forms huge flocks in its winter grounds, which include southern and western Europe, Africa, southern Asia and Australia.

The ruff is a long-necked, pot-bellied bird. This species shows marked sexual dimorphism; the male is much larger than the female (the reeve), and has a breeding plumage that includes brightly coloured head tufts, bare orange facial skin, extensive black on the breast, and the large collar of ornamental feathers that inspired this bird's English name. The female and the non-breeding male have grey-brown upperparts and mainly white underparts. Three differently plumaged types of male, including a rare form that mimics the female, use a variety of strategies to obtain mating opportunities at a lek, and the colourful head and neck feathers are erected as part of the elaborate main courting display. The female has one brood per year and lays four eggs in a well-hidden ground nest, incubating the eggs and rearing the chicks, which are mobile soon after hatching, on her own. Predators of wader chicks and eggs include mammals such as foxes, feral cats and stoats, and birds such as large gulls, crows and skuas.

Gulls and seagulls are seabirds of the subfamily Larinae. They are most closely related to terns and skimmers, distantly related to auks, and even more distantly related to waders. Until the 21st century, most gulls were placed in the genus Larus, but that arrangement is now considered polyphyletic, leading to the resurrection and revision of several genera. An older name for gulls is mews; this still exists in certain regional English dialects and is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse, and French mouette.

Gulls are usually grey or white, often with black markings on the head or wings. They normally have harsh wailing or squawking calls, stout bills, and webbed feet. Most gulls are ground-nesting piscivores or carnivores which take live food or scavenge opportunistically, particularly the Larus species. Live food often includes crustaceans, molluscs, fish and small birds. Gulls have unhinging jaws that provide the flexibility to consume large prey. Gulls are typically coastal or inland species, rarely venturing far out to sea, except the kittiwakes and Sabine's gull. The large species take up to four years to attain full adult plumage, but two years is typical for small gulls. Large white-headed gulls are usually long-lived birds, with a maximum age of 49 years recorded for the European herring gull.

Foxe Basin is a shallow oceanic basin north of Hudson Bay, in Nunavut, Canada, located between Baffin Island and the Melville Peninsula. For most of the year, it is blocked by sea ice (fast ice) and drift ice made up of multiple ice floes.

The nutrient-rich cold waters found in the basin are especially favourable to phytoplankton and the numerous islands within it are important bird habitats, including Sabine's gulls and many types of shorebirds. Bowhead whales migrate to the northern part of the basin each summer.

The East Atlantic Flyway is a migration route used by about 90 million birds annually, passing from their breeding areas in the United States, Canada, Greenland, Iceland, Siberia and northern Europe to wintering areas in western Europe and on to southern Africa. It is one of the eight major flyways used by waders and shorebirds. The migrants follow a great circle route, which is shorter although more challenging. When avoiding the barriers created by the Sahara Desert and Atlas Mountains, European honey buzzards were found to overcompensate for the winds they expected to encounter, and take a longer route than was necessary.

Wetlands International has identified key sites on the flyway in the project Wings Over Wetlands. Important sites on the flyway include:

A flyway is a flight path used by large numbers of birds while migrating between their breeding grounds and their overwintering quarters. Flyways generally span continents and often pass over oceans. Although applying to any species of migrating bird, the concept was first conceived and applied to waterfowl and shore birds. The flyways can be thought of as wide arterial highways to which the migratory routes of different species are tributaries. An alternative definition is that a flyway is the entire range of a migratory bird, encompassing both its breeding and non-breeding grounds, and the resting and feeding locations it uses while migrating. There are four major north–south flyways in North America and six covering Eurasia, Africa, and Australasia.

The Eurasian curlew or common curlew (Numenius arquata) is a very large wader in the family Scolopacidae. It is one of the most widespread of the curlews, breeding across temperate Europe and Asia. In Europe, this species is often referred to just as the "curlew", and in Scotland known as the "whaup" in Scots.

The pied avocet (Recurvirostra avosetta) is a species of wader in the Recurvirostridae family, the only member of the genus Recurvirostra found in Europe.

This characteristic wader of coastal lagoons and marshes is easily recognizable by its long, upturned bill, long legs, and striking black-and-white plumage. Measuring approximately 40 cm (16 in) in length with a wingspan of about 70 cm (28 in), it is a relatively large species that feeds on various invertebrates in water and mudflats, captured using its distinctive bill. It typically nests in colonies of 10 to 70 pairs on islets or dikes near water, laying usually four eggs in a simple, shallow scrape in the sand. Highly territorial when defending its chicks against conspecifics or predators—such as various raptors, corvids, and mammals—the pied avocet has a lifespan of about 20 years, with a record of 27 years.

Sexual dimorphism is the condition where different sexes of the same species exhibit different morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecious species, which consist of most animals and some plants. Differences may include secondary sex characteristics, size, weight, color, markings, or behavioral or cognitive traits. Male-male reproductive competition has evolved a diverse array of sexually dimorphic traits. Aggressive utility traits such as "battle" teeth and blunt heads reinforced as battering rams are used as weapons in aggressive interactions between rivals. Passive displays such as ornamental feathering or song-calling have also evolved mainly through sexual selection. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection. The opposite of dimorphism is monomorphism, when both biological sexes are phenotypically indistinguishable from each other.

Reversed sexual dimorphism (RSD) is a condition where females of a species are larger or more ornamented than the males. Species prominently displaying RSD include raptors, spiders, the leopard seal, and certain waders; in waders, it is often combined with reversed sexual dichromatism and sex role reversal.

Sefton Coast is a 4605.3 hectare (11379.9 acre) site of special scientific interest in England which stretches for 12 miles (20 km) between Southport and Waterloo, ending with Crosby Beach. The site was notified in 2000 for both its biological and geological features. It has species such as grass of Parnassus, wild orchids, rare butterflies, sand lizards, natterjack toads and waders.

Sefton Coast includes Crosby Beach, which is also the site of an art installation by Antony Gormley, called Another Place. Further north is the Formby Point National Trust site containing pinewoods and sand dunes. The whole of the area's coastline is managed as a Special Area of Conservation (SAC) by Sefton Coast Partnership because of its important wildlife reserves. The pine woods at Victoria Road have been established as a National Trust reserve for the red squirrel, which is on the endangered species list. Formby is one of several sites in Britain where the red squirrel can still be found, although the red squirrels at Formby are now threatened by the grey squirrel.

In biology, nidifugous (UK: /naɪˈdɪfjʊɡəs/ ny-DIF-yuu-gəs, US: /-jə-/ -⁠yə-) organisms are those that leave the nest shortly after hatching or birth. The term is derived from Latin nidus for "nest" and fugere, meaning "to flee". The terminology is most often used to describe birds and was introduced by Lorenz Oken in 1816. The chicks of birds in many families, such as the waders, waterfowl, and gamebirds, are usually nidifugous.

The opposite of nidifugous organisms are nidicolous (/naɪˈdɪkələs/ ny-DIK-ə-ləs; from Latin nidus "nest" and -colus "inhabiting") organisms; a nidicolous organism is one which stays at its birthplace for a long time because it depends on its parents for food, protection, and the learning of survival skills. Examples of nidicolous species include mammals and many species of birds. During the life span, the brain of a nidicolous animal expands 8–10 times its initial size; in nidifugous animals, it expands from 1.5 to 2.5 times.

Pegwell Bay is a shallow inlet in the English Channel coast astride the estuary of the River Stour north of Sandwich Bay, between Ramsgate and Sandwich in Kent. Part of the bay is a nature reserve, with seashore habitats including mudflats and salt marsh with migrating waders and wildfowl. The public can access the nature reserve via Pegwell Bay Country Park, which is off the A256 Ramsgate to Dover road.