Tuesday, February 26, 2013

Grebes in Pakistan

Grebes are small to medium-large sized freshwater diving birds. They have lobed toes, and are excellent swimmers and divers. They can run for a short distance, they are prone to falling over, since they have their feet placed far back on the body. Grebes have narrow wings

 A grebe is a member of the Podicipediformes order, a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter. This order contains only a single family, the Podicipedidae, containing 22 species in 6 extant genera.Order: Podicipediformes. Family: Podicipedidae.

 There are 20 species worldwide and 5 species  occur in Pakistan.

  1.     Little Grebe Tachybaptus ruficollis
  2.     Red-necked Grebe Podiceps grisegena
  3.     Great Crested Grebe Podiceps cristatus
  4.     Horned Grebe Podiceps auritus
  5.     Eared Grebe Podiceps nigricollis

Little Grebe   (Tachybaptus ruficollis)

The Little Grebe (Tachybaptus ruficollis) is a member of the grebe family of water birds. .It is also known as Dabchick. 

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion. It is commonly found in open bodies of water across most of its range.

The Little Grebe is a small water bird with a pointed bill. It often appears to have a 'fluffy' rear end.

The adult in summer is predominantly dark above with its rich, rufous colour neck, cheeks and flanks, and bright yellow gape. The rufous is replaced by a dirty brownish grey in non-breeding and juvenile birds. In winter, its size, buff plumage, with a darker back and cap, and “powder puff” rear end enable easy identification of this species.

 Juvenile birds have a yellow bill with a small black tip, and black and white streaks on the cheeks and sides of the neck as seen below. This yellow bill darkens as the juveniles age, eventually turning black once in adulthood.

 It readily dives when disturbed, surfacing unseen some distance away. . It can be noisy, with a distinctive whinnying trill.The Little Grebe's breeding call, given singly or in duet, is a trilled repeated weet-weet-weet or wee-wee-wee which sounds like a horse whinnying.

This species is sedentary, locally dispersive or fully migratory depending on the winter temperatures of its breeding

The species breeds in solitary pairs, the timing of breeding varying geographically and depending on the growth of emergent vegetation and water-levels. After breeding the species undergoes a flightless wing-moulting period during which it may assemble in loose groups. During the winter the species is largely solitary or occurs in small groups of 5-30 individuals The species inhabits a wide range of small and shallow wetlands usually less than 1 m deep  with rich vegetation and high densities of aquatic invertebrates, generally avoiding waters with large predatory fish. Suitable habitats include small lakes, ponds, the sheltered bays and vegetated shores  of larger freshwater, alkaline or saline lakes and reservoirs , slow-flowing rivers  and canals.

Its diet consists predominantly of adult and larval insects, especially mayflies, stoneflies, water bugs, beetles, flies, caddisflies and dragon flies, as well as molluscs , adult and juvenile amphibians  and occasionally small fish (up to 11 cm) . 

The nest is a floating platform of aquatic plant matter  submerged branches or bushes close to the edge of shallow wetlands.

Red-necked Grebe (Podiceps grisegena)

The Red-necked Grebe (Podiceps grisegena) is a migratory aquatic bird. The Red-necked Grebe is a medium-large grebe.  It is a nondescript dusky-grey bird in winter. 

The adult is 40–50 cm (15.7–19.7 in) long with a 77–85 cm (30.3–33.5 in) average wingspan and weighs 692–925 g (25–33 oz). In breeding plumage, it has a black cap that extends below the eye, very pale grey cheeks and throat, a rusty red neck, dark grey back and flanks, and white underparts. The eyes are dark brown and the long, pointed bill is black with a yellow base.

The winter plumage of the Red-necked Grebe is duskier than that of other grebes; its dark grey cap is less defined, and merges into the grey face, and a pale crescent that curves around the rear of the face contrasts with the rest of the head. The front of the neck is whitish or light grey, the hind neck is darker grey, and the yellow of the bill is less obvious than in summer.

The sexes are similar in appearance, although the male averages heavier than the female. Chicks have a striped head and breast, and older juveniles have a striped face, diffuse blackish cap, pale red neck and extensive yellow on the bill.

The Red-necked Grebe flies with its long neck extended and its large feet trailing behind the body, which gives it a stretched-out appearance. The relatively small wings are grey with white secondaries, and beat very rapidly. Its small wing area means that the grebe is unable to take off from land and needs a lengthy run across water to gain the speed needed for take-off. Like all grebes, the Red-necked is an expert swimmer; it uses its feet for propulsion underwater, and steers by rotating its legs, since its tail is too short for this purpose.

 The Red-necked is a good swimmer, a particularly swift diver, and responds to danger by diving rather than flying. The feet are positioned far back on the body, near the tail, which makes the bird ungainly on land. It dives for fish or picks insects off vegetation; it also swallows its own feathers, possibly to protect the digestive system. Red-necked Grebes attempt to evade birds of prey by diving; when feeding, dives average less than 30 seconds, although escape dives are more prolonged.

The Red-necked Grebe ingests large quantities of its own feathers, which remain in the bird's stomach. Feathers are not only swallowed by adults, mainly during self-preening, but are often fed to the young, sometimes within a day of hatching. These feathers soon decompose into a felt-like, amorphous mass. The function of the feathers in the stomach is unknown, although it has been suggested that they help to protect the lower digestive tract from bones and other hard, indigestible material.

This is one of the most vocal grebes during the breeding season, but it is mainly silent for the rest of the year. It has a loud, wailing or howling display call uooooh, given by a single bird or a pair in duet, by night or during the day, and often from cover. Long sequences of up to 60 consecutive notes may be delivered during singing encounters between rival territorial birds. A great variety of quacking, clucking, hissing, rattling and purring calls are also given, with much individual variation.

Red-necked Grebes usually nest as isolated pairs with more than 50 m (160 ft) between neighbouring nests

The Red-necked Grebe lays four or five (range one to nine) dull white or pale blue eggs, which average 3.4 cm (1.4 in) in breadth, 51 cm (2.0 in) in length, and weigh about 30.5 g (1.1 oz). Parents take turns to incubate the eggs for 21–33 days until the precocial downy chicks hatch. The young may be fed by the parents for up to 54 days after fledging. The parents do not interfere with the feeding of their chicks when they are still being carried. They immediately climb onto the parent's back, where they spend most of their time until they are 10–17 days old. Chicks are fed by the parents for several weeks.

After breeding the adults moult their wing feathers and are temporarily flightless; migration commences once the flight feathers have regrown 


Monday, February 25, 2013

Loons in Pakistan

The loons belong to family Gaviidae and of order Gaviiformes. They are the size of a large duck or small goose. There are 5 species found worldwide and only 2 species are found in Pakistan. Following are the  names of species found in Pakistan  

  1.     Black-throated Loon (Gavia arctica)
  2.     Great Northern Loon (Gavia immer)

  • Black-Throated Loon

Scientific classification

Kingdom:             Animalia
Phylum:              Chordata
Class:               Aves
Order:               Gaviiformes
Family:              Gaviidae
Genus:               Gavia
Species:             G. arctica
Binomial name :       Gavia arctica
Subspecies  :         G. a. arctica
                      G. a. viridigularis

The Black-throated Loon (Gavia arctica) is a migratory aquatic bird. They have a grey head, black throat, white underparts and chequered black-and-white mantle. Non-breeding plumage is drabber with the chin and foreneck white. Its bill is grey or whitish and dagger-shaped. In all plumage a white flank patch distinguishes this species from all other divers including the otherwise almost identical Pacific Diver. Breeding adults are 58 to 77 cm (23 to 30 in) in length with a 100 to 130 cm (39 to 51 in) wingspan, shaped like a smaller, sleeker version of the Great Northern Diver Body mass is reportedly from 2–3.4 kg (4.4–7.5 lb) .

Black-throated Loon is a specialist fish-eater and catching its prey underwater. It feeds on fish, insects, crustaceans and amphibians. It flies with neck outstretched. 

The calls include a yodeling high-pitched wail and harsh growls, similar but lower pitched than Pacific Loon.

  • Great Northern Loon

Scientific classification

Kingdom:           Animalia
Phylum:            Chordata
Class:            Aves
Order:            Gaviiformes
Family:           Gaviidae
Genus:            Gavia
Species:            G. immer
Binomial name :     Gavia immer
Synonyms :          Gavia imber

The Great Northern Loon is one of the five loon species that make up the genus Gavia, the only genus of the family Gavidae and order Gaviiformes. 

Adults can range from 61 to 100 cm (24–40 inches) in length with a 122–152 cm (4–5-foot) wingspan.The weight can vary from 1.6 to 8 kg (3.6 to 17.6 lbs). On average a Great Northern Loon is about 81 cm (32 inches) long, has a wingspan of 136 cm (54 inches), and weighs about 4.1 kg (9 lbs). Breeding adults have a black head, white underparts, and a checkered black-and-white mantle. Non-breeding plumage is brownish, with the chin and fore neck white. The bill is black-blue and held horizontally. The bill colour and angle distinguish  from other species. 

The female lays 1 to 3 eggs on a hollowed-out mound of dirt and vegetation very close to water. Both parents build the nest, sit on the egg or eggs, and feed the young.

Great Northern Loon is a specialist fish-eater, catching its prey underwater. Freshwater diets consist of pike, perch, sunfish, trout, and bass; salt-water diets consist of rock fish, flounder, sea trout, and herring. It is small sea-duck which is  black-and-white in color  which swims and dives for fish. They may dive as deep as 200 feet (60m), occasionally staying submerged for several minutes at a time.  

The bird needs a long distance to gain momentum for take-off, and is ungainly on landing. Its clumsiness on land is due to the legs being positioned at the rear of the body: this is ideal for diving but not well-suited for walking. When the birds land on water, they skim along on their bellies to slow down, rather than on their feet, as these are set too far back. 

The loon swims gracefully on the surface, dives as well as any flying bird, and flies competently for hundreds of kilometers in migration. It flies with its neck outstretched, usually calling a particular tremolo that can be used to identify a flying loon. Its flying speed is about 120 km/h (75 mph) during migration. Its call has been alternately called "haunting," "beautiful," "thrilling," "mystical", and "enchanting"

Great Northern Loon nests are usually placed on islands, where ground-based predators cannot normally access them.When approached by a predator of either its nest or itself, divers sometimes attack the predator by rushing at it and attempting to impale it through the abdomen or the back of the head or neck.