Equipped with high paws and a long neck, waders have a morphology ideally suited to their way of life. As if tailored, these two attributes allow them to grab food in water without wetting their plumage ! Portrait of a large family who look alike without sharing a bond kinship.
Identity card for waders
The term wader (Grallae) refers to a large and diverse group of water birds of morphological characteristics similar which occupy the same ecological niche. These birds take their name from their large paws reminiscent of stilts. This taxon actually designates a superorder comprising four orders :
- The gruiformes (164 species in the world) include in particular cranes, coots, bustards and moorhens;
- Ciconiiformes (19 species) include storks, herons, ombrettes, spoonbills …;
- Some pelecaniforms (118 species) including the pelican;
- The charadriiformes (316 species) include woodcock, sandpiper, plovers, knights, curlews, barges, white stilts …
Échassier, a term that has become obsolete
As noted above, waders – which once formed a order – are now divided into four different orders. The taxon has become obsolete because polyphyletic, that is, the group of animals it encompasses is defined by a resemblance that has not inherited a ancestor common. Thus, the species described as wading birds have a similar morphology and way of life without sharing any link of kinship.
Waders: similarities and differences
Despite the diversity of orders and species, the general appearance of waders remains relatively heterogeneous. In the vast majority of cases, these birds have legs tall and tapered. Their morphology is generally characterized by a long bill and neck as well as narrow, pointed wings. Waders often display different colors depending on the seasons. Their cut can vary very significantly depending on the species. The moorhen, for example, measures between 27 and 35 cm for a wingspan of 50 to 55 cm while the white stork measures approximately 1 m and deploys a wingspan of 155 to 195 cm. Still modest dimensions next to the pelicans which can reach 3 m wingspan and weigh up to 13 kilos for the Dalmatian pelican, the most imposing of all.
A physique adapted to their habitat
Waders have tall, slender legs that facilitate movement in water shallow by preventing them from getting their feathers wet. Their long, flattened fingers help them find a good stability when they frequent muddy bottoms and moss-covered rocks. Most species do not have legs webbed, an attribute that is easily dispensed with since waders walk in water, but do not swim. Even if some families are present in the land, the majority frequent aquatic such as marshes, ponds, mud flats, beaches, swamps, river banks, estuaries, coastlines, flooded meadows or even Paddy fields.
The wading bird feeds mainly in water
The wader takes advantage of its long legs when hunting in water and its long neck to capture prey passing at its feet. The diet of these birds varies depending on the species. The stork likes to feed on insects, small rodents, earthworms, fish and frogs. Scavenger and opportunistic, it can also swallow wounded or dead animals. The heron is a big fish lover who can complete his meal with amphibians, crustaceans, molluscs, aquatic invertebrates, reptiles, small rodents (mouse, shrews, voles, field mice, rats) and small birds. The shorebirds (order Charadriiformes) feed on a wide variety of invertebrates, including polychaete worms, seafood and molluscs.
The flamingo filters before eating
The flamingo is a special case. This bird filter introduces its head with a long curved beak into the water and moves it backwards. In this way, it swallows large sips of water containing small invertebrates (molluscs, crustaceans) and algae that it hurry against its beak with its large fleshy tongue. The operation allows him to evacuate thesurplus of water and swallow the food thus filtered. The flamingo also consumes insects (adults and larvae), worms, fish and seeds such as the rice.
Waders, migratory birds
While some are sedentary, most waders migrate towards regions with more pleasant winter temperatures. The populations living in northern Europe thus join the Mediterranean and North Africa before the first cold. Very impressive, the stork migration takes place twice a year. Grouped by hundreds, wading birds roam between 200 and 400 kilometers per day taking advantage of updrafts to save energy using long gliding flights. In the evening, the storks rest and set off again in the early morning until they reach their final destination: warm regions where food abounds. Males return in the month of February in order to find the ideal place to welcome their loves. There, they begin to summarily build a nest with pieces of wood. The females join them around the month ofApril to complete the shelter where they will nest.
Conservation status of waders
Waders encompass a great diversity of birds whose conservation status varies according to the species. For example, theibis, the white spoonbill and the white stork are classified in minor concern by the International Union for the Conservation of Nature (IUCN). The Dalmatian Pelican’s status changed from vulnerable to almost threatened while the black stork is considered threatened in many of its range countries (but listed as Least Concern within Europe). About the crane of Japan – one of the largest birds in the world also called red-crowned crane – it is in danger ofextinction.