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Context: A shift in migration patterns of waterbirds appears to be taking place as revealed by a recent survey conducted in the northern parts of Alappuzha.
- A detailed assessment of the survey, conducted as part of the Asian Waterbird Census 2023, shows that the population of some migratory waterbirds, especially duck species, visiting the region are falling.
- The most shocking aspect was that duck species such as Northern shoveler, Common teal and Eurasian wigeon, sighted in the previous surveys, were totally missing this time around.
- Climate change has affected the number of birds visiting the region.
About Water birds:
- Water birds are a group of birds that make up one of the most charismatic fauna which inhabit wetlands. There are many types of birds which live on and around bodies of water.
- Some water bird species are not fully adapted to the aquatic environment and only use these locations part of the year, depending on their biological cycle.
- All birds, as with all vertebrates, need water to survive. However, when we refer to water birds, it is important to distinguish them as bird species which make up part of anaquatic ecosystem. These birds require the aquatic environment for either part or all of their life cycle to survive.
- The types of water birds which make up this very broad category are incredibly varied in terms of their morphology (body shape and form), size and adaptations to their environment.
- Both migrating and non-migrating birds are in the water bird group.
- As water birds is such a general category, it has been useful to break this large group into sub-categories. They are:
- True water birds: the main characteristic of this group is the presence of certain anatomical and physiological adaptations which allow the animals to live near or on water. Examples include birds with a dense plumage combined with a thick layer of fat to allow them to maintain body temperature near very cold bodies of water. Cormorants have a special gland known as the preen gland which secretes a substance designed to keep the bird waterproof. Penguins have little blood supply to their feet, meaning they can better maintain their temperature in the rest of their body.
- Semi-aquatic water birds: although they may not have the same adaptations as other water birds, they spend at least part of the year in and around bodies of water. Being within this vicinity is necessary for them to complete their life-cycle or find the resources they require to survive.
Characteristics of water birds:
- As with all birds, water birds are vertebrate animals.
- Since these species are adapted to living on or near water, they have certain unique characteristics.
- Although the extent will vary according to the specific type of water bird, most will have interdigital membranes known as ‘webbing’ on their feet. These types of bird feetmay include:
- Pelicans: have webbing which completely covers their feet.
- Ducks: have webbing only on the base of the foot.
- Some loons/divers: develops between each individual digit.
- Water bird species also have waterproof feathers as an adaptation to the water.
- Many of them dive to find their food. Others have very long digits and claws which they can use to move through flooded areas and soft surfaces without sinking, e.g. jacanas.
- Species such as storks and herons have very long legs which allows them to search for food in shallow waters without wetting their plumage.
- Wing development is also a key factor as there are some which have adapted to use wings for swimming as well as flight. The flightless penguin has fusifrom wingswhich are only used for swimming.
- The shape of a water bird's beak is also well-adapted to aquatic living. Some species have beaks which are able to be used for feeding in waterlogged terrain.
- Shorebirds, for example, have long and thin beaks which are used to wade through shallow waters. Others, such as the duck, have a wide bill which is used to filter the water they intake.
Types and examples of water birds:
They are a group of birds associated with the sea and its coastlines. This may mean they have to spend much of their lives away from land at all, often looking for food and other resources on the sea itself.
Seabirds are a varied group which includes many different species. These include:
- Southern royal albatross (Diomedeaepomophora): one of the largest seabirds.
- Great white pelican (Pelecanus onocrotalus): has a gular pouch to capture food in the water, acting similarly to a fishing net.
- Red-footed booby (Sula sula): medium to small species which colorful beaks.
- Kelp gull (Larus dominicanus): omnivorous animals which will scavenge as well as seek prey.
- European storm petrel (Hydrobates pelagicus): nests in burrows or rock crevices which can sometimes be shared with other animals.
Anatidae, cormorants and diving birds
They are various bird species which are specialized in swimming and diving. One of the most common water birds are:
- Ducks: e.g. the mallard (Anas platyrhynchos).
- Cormorants: such as the rock shag (Phalacrocorax magellanicus). Not all cormorants are aquatic birds.
- Diving birds: like the black-necked grebe (Podiceps nigricollis). They are so-called because they are able to dive into the water to catch their prey.
In general, these birds adapt to aquatic environments, but what differentiates them from other aquatic birds is their ability to walk in water (wading). This technique is used to capture the fish that make up a substantial part of their diet. This is done thanks to their long legs, neck and beak. Within this group we can name certain herons like the grey heron (Ardea cinerea) and storks like the maguari stork (Ciconia maguari), for example.
They are those that are adapted to a wide variety of aquatic environments, such as high mountain wetlands, sandy or rocky beaches, mangroves and others. They are small or medium-sized birds with long legs, with short and wide beaks such as the little ringed plover (Charadrius dubius ), or elongated and fine, such as the Andean avocet (Recurvirostra andina).
Moorhens, jacanas, coots and the like
Most of these species use the vegetation present on the banks of lakes, ponds or other bodies of water, which is abundant where they can protect themselves and search for food. They are adapted both for swimming, as in the case of the Eurasian coot (Fulica atra), and for walking over vegetation such as wattled jacanas (Jacana jacana). Members of this group generally have bodies that allow them to move easily through dense vegetation.
Aquatic raptors and kingfishers
This group is made up of species that are not strictly aquatic or have adaptations for swimming, but use different techniques of aerial predation to capture their prey. In most cases these are fish, but they will catch land animals if possible. Examples of these birds are the Osprey (Pandion haliaetus) and the ringed kingfisher (Megaceryle torquata).
Waterfowl and other water birds
While all waterfowl are water birds, not all water birds are water fowl. Generally, they are used to describe birds in the order Anseriformes. These include ducks, swans and geese. For this reason, many people refer to waterfowl as those which are regularly hunted for game, although this is not always the case.
Like the previous group, these species do not have adaptations for life in aquatic environments, but they are associated with the vegetation surrounding water bodies. It is from here they obtain their food. The white throated dipper (Cinclus cinclus), for example, is the only passerine (referring to the order Passeriformes) that is strictly aquatic. It has a dense and waterproof plumage and other physiological adaptations that allow them to dive for several seconds and swim in the water using their wings.
Waterbirds of India:
The little egret (Egrettagarzetta) is a small white heron. Its plumage is all white. Its breeding distribution is in wetlands in warm temperate to tropical parts of Europe, Africa, Asia, and Australia. Globally, the little egret is not listed as a threatened species.
The osprey (Pandion haliaetus), sometimes known as the fish eagle, sea hawk, river hawk, or fish hawk, is a diurnal, fish-eating bird of prey. It is a large raptor,. It is found on all continents except Antarctica, although in South America it occurs only as a non-breeding migrant. The osprey is the second most widely distributed raptor species, after the peregrine falcon.
Plumbeous water redstart
The plumbeous water redstart (Rhyacornisfuliginosa) is found in South Asia, Southeast Asia and China. Males are slate blue in colour, while females are grey. The bird's common name refers to its colour which resembles lead. They tend to live near fast-moving streams and rivers.
The white-browed wagtail or large pied wagtail (Motacillamaderaspatensis) is a medium-sized bird and is the largest member of the wagtail family. They are conspicuously patterned with black above and white below, a prominent white brow, shoulder stripe and outer tail feathers. They are common in small water bodies and have adapted to urban environments where they often nest on roof tops. The specific name is derived from the Indian city of Madras (now Chennai). The white-browed wagtail is a resident breeder in India and is endemic to the Indian subcontinent.
The ruddy shelduck (Tadorna ferruginea) is a member of the duck, goose and swan family . There are very small resident populations of this species in north west Africa and Ethiopia, but the main breeding area of this species is from southeast Europe across central Asia to Southeast Asia. These birds are mostly migratory, wintering in the Indian Subcontinent. This is a bird of open country
The purple heron is a wading bird , breeding in Africa, central and southern Europe, and southern and eastern Asia. The European populations are migratory, wintering in tropical Africa; the more northerly Asian populations also migrate further south within Asia. It is a rare but regular wanderer north of its breeding range. It is somewhat smaller than the grey heron, from which it can be distinguished by its darker reddish-brown plumage, and, in adults, darker grey back. It has a narrower yellow bill, which is brighter in breeding adults. The most similarly-colored heron is the Goliath heron, which is considerably larger.
The pied kingfisher is a water kingfisher and found widely distributed across Africa and Asia. Its black and white plumage, crest and the habit of hovering over clear lakes and rivers before diving for fish makes it distinctive. Males have a double band across the breast while females have a single gorget that is often broken in the middle. They are usually found in pairs or small family parties. When perched, they often bob their head and flick up their tail.
The pheasant-tailed jacana is part of jacana group of waders that are identifiable by their huge feet and claws which enable them to walk on floating vegetation in shallow lakes, their preferred habitat. The pheasant-tailed jacana is capable of swimming, although it usually walks on the vegetation. The females are more colourful than the males and are polyandrous. The pheasant-tailed jacana breeds in India, southeast Asia, and Indonesia. It is sedentary in much of its range, but northern breeders from south China and the Himalayas migrate into peninsular India and southeast Asia.
The common merganser is a large duck, of rivers and lakes of forested areas of Europe, northern and central Asia, and North America. It eats fish and nests in holes in trees. Like the other mergansers, these fish-feeding ducks have serrated edges to their bills to help them grip their prey; they are therefore often known as "sawbills". In addition to fish, they take a wide range of other aquatic prey, such as molluscs, crustaceans, worms, insect larvae, and amphibians; more rarely, small mammals and birds may be taken.
Great crested Grebe
The great crested grebe is the largest member of the grebe family found in the Old World, with some larger species residing in the Americas. It is an excellent swimmer and diver, and pursues its fish prey underwater. The adults are unmistakable in summer with head and neck decorations. In winter, this is whiter than most grebes, with white above the eye, and a pink bill. The young are distinctive because their heads are striped black and white. They lose these markings when they become adults.The Great crested grebe breeds in vegetated areas of freshwater lakes, found across Europe and Asia. It winters on freshwater lakes and reservoirs or the coast. The crested grebe feeds mainly on fish, but also small crustaceans, insects and small frogs.
The bar-headed goosebreeds in Central Asia in colonies of thousands near mountain lakes and winters in South Asia, as far south as peninsular India. It lays three to eight eggs at a time in a ground nest. The summer habitat is high-altitude lakes where the bird grazes on short grass. The species has been reported as migrating south from Tibet, Kazakhstan, Mongolia and Russia before crossing the Himalaya.
Black Headed Ibis
The black-headed ibis or Oriental white ibis is a species of wading bird which breeds in the Indian Subcontinent and Southeast Asia from northern India, Bangladesh, Nepal and Sri Lanka east up to Japan. It occurs in marshy wetlands inland and on the coast, where it feeds on various fish, frogs and other water creatures, as well as on insects.
The cattle egretis a cosmopolitan species of heron found in the tropics, subtropics and warm temperate zones. Originally native to parts of Asia, Africa and Europe, it has undergone a rapid expansion in its distribution and successfully colonised much of the rest of the world.
The common kingfisher also known as Eurasian kingfisher, or river kingfisher, is a small kingfisher with seven subspecies recognized within its wide distribution across Eurasia and North Africa. It is resident in much of its range, but migrates from areas where rivers freeze in winter.
The green sandpiper is a small wader which breeds across subarctic Europe and Asia and is a migratory bird, wintering in southern Europe, the Indian Subcontinent, Southeast Asia, and tropical Africa.
The lesser adjutantis a large wading bird in the stork family. Like other members of its genus, it has a bare neck and head. It is however more closely associated with wetland habitats where it is solitary and is less likely to scavenge than the related greater adjutant. It is a widespread species found from India through Southeast Asia to Java.
The purple swamphen is a chicken-sized bird, with its large feet, bright plumage and red bill and frontal shield is easily recognizable in its native range. The purple swamphen prefers wet areas with high rainfall, swamps, lake edges and damp pastures. The birds often live in pairs and larger communities.