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 Post subject: Black Bittern: Shy, skulking and partly migrant
 Post Posted: Thu May 05, 2005 10:42 pm 
Black Bittern: Shy, skulking and partly migrant

by Jagath Gunawardana
@ The Island /19JUN200


Bitterns, herons and egrets are all members of the family-Ardeidae and share the same basic features. They have long painted beaks, long necks that have a kink in the middle, long legs with long toes, long, broad and round wings and short tails. Their vocal muscles are well developed and therefore can make various sounds. This family has 62 members, of which 17 have been recorded from Sri Lanka.

Our list has 13 residents, a regular winter migrant, a rare straggler and two which have been recorded once or twice only. In the case of Yellow Bittern and Black Bittern, the resident population is reinforced by arrivals during the winter migration season and can be called partly resident and partly migrant.

The Black Bittern (Dupetor flavicollis), known as Kalu Koka or Kalu Meti-koka in Sinhala is about 58cm (23 inches) in length, or about the size of a House Crow. The long neck and either be extended upto 25 cm (10 in) or more, or retracted into the shoulders until the head seems to be jutting out of the body and no neck is visible. Both sexes have prominent yellowish brown or orange-brown stripes running from the size of the throat (known as a malar stripe) that extend down along the sides of the neck and appears as a wide patch when the neck is retracted. The forneck and breast have a number of yellow, orange or white vertical streaks that have jagged edges or broken at places. In males the upperparts of the body is a dark sooty black or slaty black and black in the underparts. In females, the upperparts, especially the hind neck and back are tinged with brown as are the darker areas of the breast and abdomen. Juveniles have brown upperparts with narrow rufous borders to feathers showing as scalloped markings. The eyes are deep red. The reddish-brown beak is often tinged with black legs, dark brown or black. A small bare patch of skin around the eye is often coloured bluish-gray and hence inconspicuous.

It is mainly nocturnal and crepuscular in habits but will remain active throughout the day when the weather is dark, gloomy or rainy. It is a great skulker that prefers waterbodies with suitable dense cover nearby such as thick clumps of reads, shrubs, bushes or tangled crepers.

It prefers to either sit motionless and patiently or to wonder around slowly with deliberate, measured steps, the neck partly extended and the body horizontal, much like a crake. While walking, a bird will stop after a few steps before proceeding again. It never ventures far from cover and prefers a quiet place that allows it to do some fishing in a stealthy manner. At dusk they become quite active and can often be seen flying low over vegetation in a wetland. After alighting atop a bush or reeds, it will immediately clamber down and away without causing much disturbance and then suddenly stop and sit motionless, after reaching a place that affords it adequate cover.

When frightened or disturbed, it adopts two behaviours. One is to fly away, often uttering a louds crocking noise. The other, shared with other bitterns is to freeze on the spot and slowly and steadily extend the neck up and stretch it to the full length and look up pointing the beak towards the sky, the whole body taking a vertical pose. It blends with the surroundings and the markings on the neck and breast making the camouflage perfect and will remain motionless. It is amazing to see how easily and effortless it makes this change from the normal posture to this freezing posture. A bird remaining still in this posture can be approached quite close, if it is done cautiously without the bittern realizing that the person is making a straight approach at it. After a while, it will retract the neck a little and look around carefully before coming back to the normal pose and moving away.

The flight is fast, silent and powerful with steady, strong beats of the large round wings. In flight, the neck is pulled in with only the head being visible and the long legs trail behind the short tail. The usual call note is a loud "crock" that is repeated several times in flight but is usually silent when at rest or walking.

The loud booming call that is mentioned in books has never been heard by me. Food consists of small aquatic animals such as fish, frogs and insects. It shoots out the neck and grasp the prey between the mandibles of the beak and often swallowed immediately. If a larger creature is caught, a bird may fly away with the prey held in the beak to a safer place to consume it. Though it has long legs and toes, it can get a good grasp of thin branches and clamber among masses of tangled vegetation or reeds quite nimbly.

The Black Bittern is found throughout the low country, wet and dry zones and the lower hills. W.E. Wait (1930) reports meeting them at Bogawantalawa at an altitude of 4000 feet. A large number migrate to Sri Lanka during the winter period. This partial migration was first mentioned by Vincent Legge (1880) and has been confirmed by all subsequent works. During my observations in the Eastern Province, it was met with infrequently in smell numbers and no perceptible change in numbers was ever observed during the winter months. In the wet zone, it is uncommon during the other months but show a marked and sudden increase during the winter months. This increase builds up in October and November when large numbers may be encountered suddenly in areas where it could have been difficult to spot a single bird even a week ago. Large numbers tend to be seen in suitable habitats during this initial build-up and a few will be found where they are not found during the other times. Their numbers may decrease somewhat in some places by December. This may be due to individuals moving away to other suitable places or thinning out to a larger area. The increased numbers continue till March when the numbers may decrease suddenly and then reduce gradually till mid-or late - April, until very few remain.

These observations over the years show that the resident population is augmented by new arrivals during the winter and that this is clearly seen in the low country wet zone and the adjoining hills but not in the eastern side. It suggests that the migrant Black Bitterns would be arriving in Sri Lanka through the Western Migration route. During the arrival period a bird may find refuge temporarily in a thicket in a home garden and may even remain for some time if there is a pond nearby, or one may even blunder into a house at night.

Some of these are from Colombo and suburbs every year. A bittern that finds the way into a house or found tired or injured has to be handled with utmost care because the sharp, pointed beak, propelled by the sudden recoil of the neck can inflict deep and dangerous wounds. The beak should be always pointed away from the body of the person and held firmly with one hand. It is important to remember that bitterns select a bright or glimmering thing as a target which could well be the eyes of the person.

Little is known about the breeding of the Black Bittern in Sri Lanka. According to Wait (1930) it breeds about April and he has found two nests in the North Central Province during this month. They had been on low thorny trees within 3 feet of the tank and the full clutch has consisted of four, very pale, sea-green eggs. G.M. Henry (1971) only makes reference to these records probably due to him not encountering a nest. Fishermen who go into wetlands to catch the Muttell (Loola in Sinhala) occasionally report seeing a nest of this species. The only nest seen by me was at the Kotte (Sri Jayawardhanapura) Sanctuary in late April 1987. It had four white eggs, according to the person who reported it to me. The nest was on a small thicket in the middle of a marshy area, well-concealed and partly visible from a distance as a mass of twigs, with the parents in attendance. It was at a difficult place to access and no effort was made to approach it because it could have disturbed the parents.

Observations could not be continued due to an examination which was only a few days away. In early May 1992, another nest had been seen by a person at another part of the Kotte Sanctuary but had not reported it to anyone at the time as he was unaware that it was a rare finding. In both instances, it was seen that nests were seen at the commencement of the South-Western Monsoon. The shy nature of the bird and its nesting habits makes it difficult to spot a nest and it is compounded by it nesting during the monsoon, making it virtually impossible to locate or approach a nest.

The Black Bittern has a wide range of distribution in the Indian sub-continent, South-East Asia, Thailand, Burma, China, to New Guinea and Australia.

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