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Striated Heron

From Opus

Photo by obasanmiRanweli, Sri Lanka
Photo by obasanmi
Ranweli, Sri Lanka
Butorides striata

Contents

[edit] Identification

L. 35-45 cm (14-18 in)

  • Black cap
  • Whitish line from central chest to chin
  • Whitish line on central underparts is edged and/or mottled rufous in many races.
  • Blackish wings with greyish, dull dark greenish or brownish edging
  • Belly, flanks, neck and head are greyish in most races
    • Brownish in some Australasian subspecies.
Photo by Dr Manjeet SinghPandamaran, Port Klang, Selangor, Malaysia
Photo by Dr Manjeet Singh
Pandamaran, Port Klang, Selangor, Malaysia
  • Yellow, bluish, or blackish lores
  • Yellowish or reddish legs
    • Brighter when breeding
  • Yellow eyes
  • Flight low, with quick beats of wings. Neck folded, feet protrude from tail.
  • Black bill
    • Often with yellow lower mandible

Dumpy little heron with a large head and bill. General colour blackish green; grey below; throat white; down foreneck dependent on subpecies; erectile feathers on crown, at rest extending down nape, scapulars and wing-feathers margined with white, or buffy-white ; hind-neck, sides of face, abdomen, sides of body, axillaries, and under wing-coverts grey, somewhat paler on the vent and under tail-coverts ; throat and fore-neck white with an irregular line of dark chestnut-brown feathers down the middle which spreads out and becomes pale rufous on the breast ; outer edge of wing white. Bare parts: iris yellow, deep orange when breeding; lores green to blue, yellow when breeding; bill black above, yellow green below with black tip, entirely black when breeding; feet and legs grey brown in front, yellow behind, yellow to reddish orange when breeding.

Female According to A.D. Forbes-Watson in ‘Notes on birds observed in the Comoros on behalf of the Smithsonian Institution’gender can be told by colour of the legs, yellow in females and red in males, though this statement has rarely been repeated.

Juvenile

  • Brown
  • Whitish-buff streaking on underparts, neck and head
  • Spotting on wings
  • According to some authors the amount and intensity of the streaking on the chest is a sign of the birds age, with streaks fading with age.

[edit] Races

Two Australian races, macrorhyncha and stagnatilis, occurs in a grey and a rufous morph, while the normally grey nominate also occurs in a rare rufous-necked morph (confirmed for Peru and Bolivia; possibly also elsewhere).

[edit] Similar Species

B. s. macrorhynchus (rufous morph)Photo by NeilNear Sydney, Australia
B. s. macrorhynchus (rufous morph)
Photo by Neil
Near Sydney, Australia

Adults are generally distinctive. Rufous-necked morph of nominate race is paler, and has a greyer belly than the Green Heron (limited overlap between the two in coastal Venezuela, Trinidad & Tobago, coastal northern Colombia and eastern Panama).

Possible hybrids between the Striated and the Green showing intermediate plumage have been recorded. Juvenile of Striated, Green and Lava Heron are virtually inseparable.

[edit] Distribution

Widespread in sub-Saharan Africa (except far south), warmer parts of Asia, coastal northern and eastern Australia, South America (except far south and the Andes), and islands in the Indian Ocean and Pacific Ocean. See Taxonomy for further information on range. Most races sedentary or with local dispersal only, but two Asian races, amurensis and actophilus, migrate south following breeding.

Generally common and widespread. Some localized races are rarer, and it has been estimated that only around 100 individuals remain of the subspecies patruelis.

[edit] Taxonomy

B. s. striataPhoto by BirdsPeruLima, Peru
B. s. striata
Photo by BirdsPeru
Lima, Peru

The scientific name was recently corrected from Butorides striatus to Butorides striata. This species was previously placed in the genus Ardeola.

Also know as: Little Heron, Little Green Heron, Green-backed Heron and Mangrove Heron. Sometimes also called the Green Heron, leading to easy confusion with the mainly North American Butorides virescens.

Numerous races exist:

[edit] American races

Nominate (striata) occurs through most of South America, except for the far south and the Andes. Also in eastern Panama and Trinidad (Tobago mainly has Green Heron).

[edit] African and Middle East races

B. s. brevipes is found on the Red Sea coasts south to Somalia, atricapilla from the rest of mainland Africa south of the Sahara, rutenbergi from Madagascar, crawfordi on the Aldabra and Amirante Islands, rhizophorae in the Comoros, degens in the Seychelles and javanica on Reunion, Mauritius, and Rodrigues (this race also in Oriental region, see following). Race 'atricapilla' can be identified by the following: Streaks on the throat tawny rufous. Grey ornamental plumes on the back, wing coverts edged with sandy buff, crown is greenish black. Upper mandible dusky, lower mandible greenish yellow with dusky margins. Iris light yellow. 'rutenbergi': Similar to atricapilla but generally darker, with a redder neck, reminiscent of the North American Green Heron.

[edit] Oriental races

B. s. chloriceps is found in India and Sri Lanka, albolimbata on Diego Garcia, Chagos Archipelago, and Maldives, javanica in Burma and Thailand south to the Greater Sundas (this race also in African region, which see), amurensis is found in north-east Asia and northern China (winters in SE Asia south to Sumatra and Philippines), actophila from southern China to northern Thailand (winters in Sumatra, Borneo, and Nicobar Is.), spodiogaster in Sipura and north Pagai, western Sumatra islands, the Andaman and Nicobar Islands, carcinophila on Taiwan, the Philippines, and Sulawesi, steini in the Lesser Sundas and moluccarum on the Moluccas. Race 'javanica' can be identified by the following: Throat and foreneck uniform or mottled with blackish, but never streaked with tawny rufous. Plumes with white-shaft lines, scapular feathers green, sometimes with grey tips. Wing coverts green with buff margins. Below the eye there is a streak of greenish black extending along the ear coverts, edged with a white streak on the top, a second streak from the lower mandible along the cheeks. Upper mandible black with longitudinal yellow stripe below the nostrils. Facial skin and legs green. 'amurensis': As javanicus but stockier (wing 17-22cm, compared to 17cm for javanicus) with a coarser bill. 'spodiogsater': Throat and cheek-stripe ashy or brown, not distinctly indicated, abdomen rusty. Sides of neck and sides of body dark, sooty, slate colour; cheeks and ear coverts also slate colour. Very similar to B.s.stagnatilis, but no so dingy underneath. Bill black, lower portion of lower mandible, from base to tip, edged pale horny

[edit] Australasian races

B. s. papuensis occurs in coastal north New Guinea and islands, idenburgi in the interior of north New Guinea, rogersi in coastal Western Australia from Ashburton River to Shark Bay, cinerea from King Sound to De Grey River, Western Australia, stagnatilis from Melville Island to Groote Eylandt and the McArthur River, littleri in coastal north Queensland and southern New Guinea, macrorhyncha from southern Queensland to New South Wales and on New Caledonia and the Loyalty Isles, solomonensis in New Hanover, New Ireland, the Solomon Islands, Santa Cruz, the Torres Islands, Banks Islands, New Hebrides and western Fiji Islands and patruelis in Tahiti, Society Islands. Race 'stagnatilis' can be identified by the following: Sides of neck washed with rusty brown like the sides of the body, abdomen, cheeks and ear coverts rusty brown too.

Some authorities includes the Green Heron and the Galapagos Heron as subspecies.

[edit] Habitat

The species shows a preference for forested water margins such as mangrove-lined shores and estuaries, or dense woody vegetation fringing ponds, rivers, lakes and streams. Other suitable habitats include river swamps, canals, artificial ponds, salt-flats, mudflats, tidal zones, exposed coral reefs, reedbeds, grassy marshland, pastures, rice-fields and other flooded cultivation. In plains to an altitude of 750m, occasionally upto 1300m. There have also been a few records of some birds in a savannah woodland, where the bird would hunt tadpoles in shallow pools, far away from permanent water.

[edit] Behaviour

This species is extremely territorial and often forages and nests alone, occasionally in good conditions the birds nest in loosely spaced groups of 5-15 pairs, or even rarer: very large groups of several hundred pairs. This territoriality extends to their foraging behaviour, where birds will stand on floating debris, hunting the trapped insects, until the debris leaves their immediate territory, at which they will return to the bank. Often seen watching water from a shallow perch for food, also sometimes in rice fields. When hunting the birds will occasionally use ‘bait’ dropping a feather or leaf on the water and spearing the fish that come to investigate, there have also been reports of birds dropping bread scraps in the water. Another interesting foraging technique is using a floating piece of debris as a ‘base’ from which they can float into deeper water, and have been observed diving into the water to a considerable depth in order to catch a fish. Although they forage throughout the day their activity spikes in the evening and morning. They nest near water in broadleaf forest or shrub canopy shelter. Young Birds will occasionally give a display if threatened, which consists of stretching their neck, and pointing their bill up. An additional threat display is detailed and illustrated at http://www.besgroup.org/2012/08/15/aggressive-behaviour-of-striated-heron-fight-flight-or-fright/ . Adults will freeze when disturbed; standing motionless with their bills at 45o. Tame around habitated areas.

[edit] Diet

Diet is mainly fish, frogs, snails and insects. Though stomach content analysis contained fragments of Linmocharis (A common wetland plant) and insect fragments

[edit] Breeding

The Breeding season varies according to the location, but in the tropics occurs during heavy rains. Nest is a small, shallow structure of twigs, placed hidden among the braches of trees and scrubs (especially mangroves, Rhizophora spp. and Avicennia spp., or Allocasuarina spp. , Myoporum spp. , Callistemon spp., Hibiscus spp., Casuarina spp., Syzygium spp.and Inga spp.) between 0.3 and 10m above the water, ridiculously small for the bird, normally being a few dry sticks put together. Clutch of 3-5 eggs, both the male and female co-incubate, through a period of 20-22 days. Eggs are pale blue and measure 36x28mm. In China the breeding season is April to September, wintering around the coastal areas of Jiangsu, but numbering less than one hundred.

[edit] References

[edit] External Links


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