Dwarf Bittern (Butorides sturmii)

Dwarf Bittern

[order] CICONIIFORMES | [family] Ardeidae | [latin] Butorides sturmii | [authority] Wagler, 1827 | [UK] Dwarf Bittern | [FR] Blongios de Sturm | [DE] Grauruckendommel | [ES] Avetorillo Plomizo | [NL] Dwergroerdomp

Subspecies

Monotypic species

Genus

Butorides is a genus of small herons. It contains three similar species, the Green Heron or Green-backed Heron, Butorides virescens, the Dwarf Bittern (Butorides sturmii), and the Striated Heron, Butorides striatus. A fossil species, Butorides validipes, is known from the Early Pleistocene of Florida. Adults of both extant species are about 44 cm long, and have a blue-black back and wings, a black cap and short yellow legs. Juveniles are browner above and streaked below, and have greenish-yellow legs. The species have different underpart colours, chestnut with a white line down the front in Green Heron, and white or grey in Striated. Both breed in small wetlands on a platform of sticks often in shrubs or trees, sometimes on the ground. Butorides herons stand still at the water’s edge and wait to ambush prey. They mainly eat small fish, frogs and aquatic insects. They sometimes drop food on the water’s surface to attract fish.

Physical charateristics

The Dwarf Bittern has a height of 25 cms and weighs around 140 gms. The head is coloured grey, black while the bill is coloured grey. The Ixobrychus sturmii has a grey coloured throat, yellow legs and a grey, black coloured back. The eyes are yellow.

The male Ixobrychus sturmii has physical features that are slightly different from the female bird.


wingspan min.: 0 cm wingspan max.: 0 cm
size min.: 27 cm size max.: 30 cm
incubation min.: 14 days incubation max.: 15 days
fledging min.: 13 days fledging max.: 15 days
broods: 1   eggs min.: 2  
      eggs max.: 6  

Range

Africa : widespread

Habitat

It uses a variety of habitats, but shows a preference for thickets and forests characterised by fluctuating water levels. It frequents the margins of freshwater rivers, streams, lakes, reservoirs, ponds and pools overhung with dense foliage, marshes with grasses or reeds, seasonally flooded areas, mangroves, rice-fields, and open grassy swamps with bulrushes or papyrus.

Reproduction

The nest is a stick platform positioned 0.5-4 m high on horizontal or hanging branches of trees and bushes1 that overhang water or stand in flooded areas. They breed from December to March with incubation lasting from 18-26 days.

Feeding habits

Its diet consists predominantly of grasshoppers and frogs, but it will also take water beetles, small fish, crabs, spiders and snails.

Video Dwarf Bittern

httpv://www.youtube.com/watch?v=mPw6x5Lq3J8

copyright: Martin Kennewell


Conservation

This species has a large range, with an estimated global Extent of Occurrence of 12,000,000 km2. It has a large global population estimated to be 25,000-100,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern.
Breeds from Senegal east to Ethiopia and south, mainly through the eastern half of Africa, to the Cape. Absent from the arid areas of the south-west. Generally rare and seldom seen. A partial migrant occurring in the northern part of the range during the May-September wet season. An extremely rare vagrant to the Western Palearctic and recorded only in the Canary Islands. There are four acceptable records, although the first two of these, both from Tenerife, one in the late 19th Century and the other in the 1970s, have yet to be ratified by the relevant recording bodies. The first accepted record was a bird photographed on Gran Canaria in January 2000. The most recent was a bird photographed at Erjos on Tenerife in August 2002 and present until April 2003. In addition there have been several unsubstantiated reports from Lanzarote and Allegranza and a 19th Century record of two birds shot in France
Dwarf Bittern status Least Concern

Migration

This species is an intra-African migrant, its movements related to changes in water level due to seasonal rainfall

Distribution map

Dwarf Bittern distribution range map

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