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.
The ruff forages in wet grassland and soft mud, probing or searching by sight for edible items. It primarily feeds on insects, especially in the breeding season, but it will consume plant material, including rice and maize, on migration and in winter. Classified as "least concern" on the IUCN Red List criteria, the global conservation concerns are relatively low because of the large numbers that breed in Scandinavia and the Arctic. However, the range in much of Europe is contracting because of land drainage, increased fertiliser use, the loss of mown or grazed breeding sites, and over-hunting. This decline has seen it listed in the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA).
Taxonomy and nomenclature The ruff is a wader in the large family Scolopacidae, the typical shorebirds. Recent research suggests that it is in a near-basal position in the genus Calidris, the sister taxon to all of the species except for the knot group (red knot, great knot and surfbird). It has no recognised subspecies or geographical variants.
This species was first described by Carl Linnaeus in his Systema Naturae in 1758 as Tringa pugnax. It was moved to the monotypic genus Philomachus by German naturalist Blasius Merrem in 1804. More recent DNA research has shown it fits comfortably into the wader genus Calidris. The genus name comes from the Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific epithet refers to the aggressive behaviour of the bird at its mating arenas — pugnax from the Latin term for "combative".
The original English name for this bird, dating back to at least 1465, is the ree, perhaps derived from a dialectical term meaning "frenzied"; a later name reeve, which is still used for the female, is of unknown origin, but may be derived from the shire-reeve, a feudal officer, likening the male's flamboyant plumage to the official's robes. The current name was first recorded in 1634, and is derived from the ruff, an exaggerated collar fashionable from the mid-sixteenth century to the mid-seventeenth century, since the male bird's neck ornamental feathers resemble the neck-wear.
Description
The ruff has a distinctive pot-bellied appearance, with a small head, medium-length bill, longish neck and heavy body. It has long legs that are variable in colour, being dark greenish in juveniles, pink to orange in adults with some males having reddish orange legs only during the breeding season. In flight, it has a deeper, slower wing stroke than other waders of a similar size, and displays a thin, indistinct white bar on the wing, and white ovals on the sides of the tail. The species shows sexual dimorphism. Although a small percentage of males resemble females, the typical male is much larger than the female and has an elaborate breeding plumage. Males are long with a wingspan, and weigh from , the largest species in the genus Calidris. In the May-to-June breeding season, the male's legs, bill and warty bare facial skin are orange, and he has distinctive head tufts and a neck ruff. These ornaments vary on individual birds, being black, chestnut or white, with the colouring solid, barred or irregular. The grey-brown back has a scale-like pattern, often with black or chestnut feathers, and the underparts are white with extensive black on the breast. The extreme variability of the main breeding plumage is thought to have developed to aid individual recognition in a species that has communal breeding displays, but is usually mute.
Outside the breeding season, the male's head and neck decorations and the bare facial skin are lost and the legs and bill become duller. The upperparts are grey-brown, and the underparts are white with grey mottling on the breast and flanks.
Females, or "reeve", are long with a wingspan, and weighs from . In breeding plumage, they have grey-brown upperparts with white-fringed, dark-centred feathers. The breast and flanks are variably blotched with black. In winter, the females' plumage is similar to that of the male, but the sexes are distinguishable by their size. The plumage of the juveniles resembles the non-breeding adult, but has upperparts with a neat, scale-like pattern with dark feather centres, and a strong buff tinge to the underparts.
Adult male ruffs start to moult into the main display plumage before their return to the breeding areas, and the proportion of birds with head and neck decorations gradually increases through the spring. Second-year birds lag behind full adults in developing breeding plumage. They have a lower body weight and a slower weight increase than full adults, and perhaps the demands made on their energy reserves during the migration flight are the main reason of the delayed moult.
Ruffs of both sexes have an additional moult stage between the winter and final summer plumages, a phenomenon also seen in the bar-tailed godwit. Before developing the full display finery with coloured ruff and tufts, the males replace part of their winter plumage with striped feathers. Females also develop a mix of winter and striped feathers before reaching their summer appearance. The final male breeding plumage results from the replacement of both winter and striped feathers, but the female retains the striped feathers and replaces only the winter feathers to reach her summer plumage. The striped prebreeding plumages may represent the original breeding appearance of this species, the male's showy courtship feathers evolving later under strong sexual selection pressures.
Adult males and most adult females start their pre-winter moult before returning south, but complete most feather replacement on the wintering grounds. In Kenya, males moult 3–4 weeks ahead of the females, finishing before December, whereas females typically complete feather replacement during December and early January. Juveniles moult from their first summer body plumage into winter plumage during late September to November, and later undergo a pre-breeding moult similar in timing and duration to that of the adults, and often producing as brightly coloured an appearance.
Two other waders can be confused with the ruff. The juvenile sharp-tailed sandpiper is a little smaller than a juvenile female ruff and has a similar rich orange-buff breast, but the ruff is slimmer with a longer neck and legs, a rounder head, and a much plainer face. The buff-breasted sandpiper also resembles a small juvenile ruff, but even the female ruff is noticeably larger than the sandpiper, with a longer bill, more rotund body and scaly-patterned upperparts.
Distribution and habitat
The ruff is a migratory species, breeding in wetlands in colder regions of northern Eurasia, and spends the northern winter in the tropics, mainly in Africa. Some Siberian breeders undertake an annual round trip of up to to the West African wintering grounds. There is a limited overlap of the summer and winter ranges in western Europe. The ruff breeds in extensive lowland freshwater marshes and damp grasslands. It avoids barren tundra and areas badly affected by severe weather, preferring hummocky marshes and deltas with shallow water. The wetter areas provide a source of food, the mounds and slopes may be used for leks, and dry areas with sedge or low scrub offer nesting sites. A Hungarian study showed that moderately intensive grazing of grassland, with more than one cow per hectare (2.5 acres), was found to attract more nesting pairs. When not breeding, the birds use a wider range of shallow wetlands, such as irrigated fields, lake margins, and mining subsidence and other floodlands. Dry grassland, tidal mudflats and the seashore are less frequently used. The density can reach 129 individuals per square kilometre (334 per square mile), but is usually much lower.
The ruff breeds in Europe and Asia from Scandinavia and Great Britain almost to the Pacific. In Europe it is found in cool temperate areas, but over its Russian range it is an Arctic species, occurring mainly north of about 65°N. The largest numbers breed in Russia (more than 1 million pairs), Sweden (61,000 pairs), Finland (39,000 pairs) and Norway (14,000 pairs). Although it also breeds from Britain east through the Low Countries to Poland, Germany and Denmark, there are fewer than 2,000 pairs in these more southerly areas.
It is highly gregarious on migration, travelling in large flocks that can contain hundreds or thousands of individuals. Huge dense groups form on the wintering grounds; one flock in Senegal contained a million birds. A minority winter further east to Burma, south China, New Guinea and scattered parts of southern Australia, or on the Atlantic and Mediterranean coasts of Europe. In Great Britain and parts of coastal western Europe, where the breeding and wintering ranges overlap, birds may be present throughout the year. Non-breeding birds may also remain year round in the tropical wintering quarters. The Ruff is an uncommon visitor to Alaska (where it has occasionally bred), Canada and the contiguous states of the US, and has wandered to Iceland, Middle America, northern South America, Madagascar and New Zealand. It has been recorded as breeding well south of its main range in northern Kazakhstan, a major migration stopover area.
The male, which plays no part in nesting or chick care, leaves the breeding grounds in late June or early July, followed later in July by the female and juveniles. Males typically make shorter flights and winter further north than females; for example, virtually all wintering ruffs in Britain are males, whereas in Kenya most are females. Many migratory species use this differential wintering strategy, since it reduces feeding competition between the sexes and enables territorial males to reach the breeding grounds as early as possible, improving their chances of successful mating. Male ruffs may also be able to tolerate colder winter conditions because they are larger than females.