Malagasy Pond-Heron

识别特征

Malagasy pond herons grow to 45–50 cm (18–20 in) in height and anywhere from 250–350 g (9–12 oz) in weight. There is not a large variation in weight between the sexes as they are quite similar in bone body structure. feather, eye, and bill colour are determined by life stage (chick, juvenile, and adult) and reproductive status.<p>The adults appearance can be split into the non-breeding plumage and the breeding stage. When the species is not breeding, the crown and the posterior are a colour mixture of buff and black with brown prominent over the other parts of the body. The bill is predominately green with a black tip whilst the iris is yellow. The flight feathers are clearly seen in flight and for the most part are white. The feathers on the lower mantle and upper scapulars are loosely structured and elongated. Moreover, the lower foreneck feathers are split into fine elongated tips which cover the upper breast.<p>The primary difference of appearance in the breeding stage is the dominance of a snow white colour over the body a bill of a deep azure blue. When coming out of breeding, an intermediate plumage emerges on the back, and dense plumes sprouting on areas such as the neck and breast.<p>Prior to adulthood, the Malagasy pond heron will possess a juvenile plumage just before leaving the nest, lasting a few weeks. The juvenile differs from the adult in having a dull orange bill and pale green eyes. The one distinguishing feature of the chick is its thick buff yellow down.

分类信息

The Malagasy pond heron was first described in 1860 by German physician and ornithologist Gustav Hartlaub. The species is monotypic, without distinct subspecies.

学名

Ardeola idae

命名信息

(Hartlaub, 1860)

目

Pelecaniformes

科

Ardeidae

属

Ardeola

分布与栖息地

The Malagasy pond herons breed in Madagascar, Réunion and the Seychelles. During the non-breeding season, they migrate to eastern mainland Africa, in Kenya, Tanzania, Uganda, Rwanda, Burundi, DR Congo, Malawi, Zambia, Zimbabwe and Mozambique. In Madagascar, some of the locations where commonly observed include Lake Alarobia and Tsimbazaza Park (both near Antananarivo), wetlands around Ampijoroa and at Berenty. As a result, their estimated area of occurrence is 553,000 km2 (214,000 sq mi). They occupy a broad range of Madagascan habitats that include small grassy marshes, lakes, ponds, streams, and rice fields. Those that populate the Aldabra region are commonly located in mangroves, inland pools, and lagoon shores. It can be found from sea level to elevation levels up to 1,800 metres (6,000 ft).

繁殖区

AF : Madagascar and Aldabra I.

非繁殖区

c, e AF

迁徙

Complete migrants

行为

One of the key behavioural habits of the Malagasy pond heron is its yearly migratory pattern. It migrates from Madagascar to the eastern mainland of Africa in May and journeys back to its breeding range in October. Those that have not matured into adult life remain in the non-breeding areas, as there is no benefit in travelling to the breeding zone.<p>In terms of interaction, this species is very territorial and communication with other rival birds is limited. As such, they will remain at least 10 m (30 ft) apart if nesting or in flight due to their inconspicuous nature. One observation found two Malagasy pond herons fighting, grasping at each other's bills in the motion of flight. In Africa, instances such as this are scarce as there is rarely more than two on the same body of water.<p>Nesting tends to be done along the coast and foraging for food is performed well inland, away from the nests. In fact, the closest that an individual heron will get to another apart from breeding is during roosting in their nests. Habitat degradation has resulted in closer roosting and has become integrated with other heron species such as cattle egrets and squacco herons.

保护状况

The conservation status of the Malagasy pond heron has changed dramatically over the last few decades. In 1988, this species was classified as near threatened according to IUCN's red list, but continued pressure on the population resulted in a move to the vulnerable category in 2000. In 2016, it was further upgraded to endangered. The main threats are collection of eggs and young at their breeding colonies and degradation of their wetland habitats.

种群趋势

declining