Intermediate Egret (Egretta intermedia)

Intermediate Egret

[order] CICONIIFORMES | [family] Ardeidae | [latin] Egretta intermedia | [authority] Wagler, 1829 | [UK] Intermediate Egret | [FR] Aigrette intermediaire | [DE] Mittelreiher | [ES] Garceta intermedia | [NL] Middelste Zilverreiger

Subspecies

Monotypic species

Genus

Egretta is a genus of medium-sized herons, mostly breeding in warmer climates. Representatives of this family are found in most of the world, and the Little Egret, as well as being widespread throughout much of the Old World, has now started to colonise the Americas. Little Egret Egretta garzetta in Kolleru, Andhra Pradesh, India.These are typical egrets in shape, long-necked and long-legged. There are few plumage features in common, although several have plumes in breeding plumage; a number of species are either white in all plumages, have a white morph (e.g. Reddish Egret), or have a white juvenile plumage (Little Blue Heron). The breeding habitat of Egretta herons is marshy wetlands in warm countries. They nest in colonies, often with other wading birds, usually on platforms of sticks in trees or shrubs.

Physical charateristics

The Intermediate Egret is a medium sized white egret. It looks similar to the Great Egret, but is smaller, has a more rounded head and the orange bill is shorter and not so acute angled. The neck is about the same length as the body. In breeding plumage they have deep pink to red bill, blue-green facial skin and long breast plumes and long wing plumes extending beyond the tail.

Listen to the sound of Intermediate Egret

[audio:http://www.planetofbirds.com/MASTER/CICONIIFORMES/Ardeidae/sounds/Intermediate Egret.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 105 cm wingspan max.: 115 cm
size min.: 56 cm size max.: 72 cm
incubation min.: 24 days incubation max.: 27 days
fledging min.: 33 days fledging max.: 37 days
broods: 1   eggs min.: 2  
      eggs max.: 6  

Range

Oriental Region, Africa, Australasia : widespread.

Habitat

The species inhabits lowlands from sea-level to 1000 m in Sumatra, and 1450 m in Nepal. It shows a preference for sheltered flood-plains and seasonal wetlands with water less than 80 mm deep and emergent grasses, herbs, sedges, reeds or rushes and abundant aquatic vegetation (generally avoiding areas where vegetation is too thick for feeding). Such habitats include seasonally flooded marshes, inland deltas (e.g. Okavango Basin, Botswana), ponds, swamp forest, freshwater swamps, pools, rivers, streams, rice-fields, the margins of freshwater, brackish and saltwater lakes, wet meadows, and flooded and dry pasture near water. It occurs less often in coastal habitats, but may roost in mangrove swamps, and frequents mudflats, tidal estuaries, coastal lagoons, saltmarshes, and tidal streams and rivers.

Reproduction

Timing of breeding varies regionally, but is usually centred around the wet season. During this time, the intermediate egret builds its nest amongst those of other herons and waterbirds, with colonies occasionally numbering as many as several thousand. The nest is a shallow stick platform and is positioned three to six meter above the ground in a tree standing over water or reedbeds. Two to six eggs are laid and incubated for 21 to 27 days. The young flede after about 35 days. In Australia bigamy has been recorded.

Feeding habits

In aquatic habitats the diet of this species consists predominantly of fish less than 10 cm long (including eels, perch Macquaria, gudgeon and mosquitofish Gambusia), as well as frogs, crustaceans (e.g. crayfish) and aquatic insects (e.g. leeches, water bugs and dragonfly larvae). It will also take terrestrial prey in drier habitats including grasshoppers mole crickets, bugs and beetles, snakes, spiders, lizards and exceptionally birds.

Video Intermediate Egret

httpv://www.youtube.com/watch?v=qJbk5sw8SLM

copyright: Tom Tarrant


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
This species has declined markedly in Japan since the 1960s due to pollution and the disturbance of nesting colonies. The species is also threatened in the Northern Territory of Australia by the degradation of flood-plain habitats owing to grazing, burning, invasion by introduced plants (particularly Mimosa pigra and Salvinia molesta), reduced water flows from drainage and water diversion for irrigation, levee breaking by feral buffalo (allowing salt intrusion and accumulation of tidal sediment), clearing of swamp forest, and pollution from mineral extraction.
Intermediate Egret status Least Concern

Migration

Mainly sedentary with some nomadic movements; extensive post-breeding dispersal. N populations of nominate race migratory: birds leave Japan in Sept/Oct to winter in Philippines and SE Asia, returning to colonies in Apr; often some birds overshoot and reach SE USSR or North Korea. Australian birds apparently sedentary, but great variations in numbers suggesting significant dispersal or perhaps migration, e.g. 1 bird ringed in Victoria recovered in Irian Jaya (W New Guinea), and possible movements N-S along central York Peninsula. In Africa mainly sedentary, although some evidence of possible migration, e.g. 1 bird ringed in South Africa recovered in Zambia, and species is seasonal visitor to Sierra Leone and S Nigeria. Accidental to Cape Verde Is, C Asia, New Zealand and Marion I (S Indian Ocean).

Distribution map

Intermediate Egret distribution range map

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