THE BITTERN – MATUKU-HUREPO.

Forest and Bird, Issue 48, 1 May 1938, Page 3

THE BITTERN - MATUKU-HUREPO.

(By R. A. Falla.)

(Botaurus poeciloptilus.)

THE boom of the Bittern is a sound associated with marshlands in many parts of the world, and in New Zealand a representative species is still common in suitable districts. Indeed, the only reason why this morose-look-ing bird is not more frequently seen is that the colour of its plumage matches so closely the surrounding vegetation and the bird’s behaviour is often such as to aid the deception. In the cover illustration published with this article attention is focused on the details of the bird, but an observer who has come across Bitterns in their native haunts will know how difficult it is to make out the details of the bird’s shape and plumage. As a means of protection, the Bittern has a curious way of assuming the shape of a stick or stump with its beak pointing upwards and feathers close pressed to its sides. Should it happen to be amongst long grass or rushes it becomes almost indistinguishable. Occasionally, however, this attitude is adopted in the open, and apart from looking rather like a stump of wood, the bird is then quite conspicuous. The Bittern obtains all its food from the swamp or from the moist lands adjacent. While the reduction in the area of swamp country must have considerably decreased the total number of Bitterns during the past century, a plentiful food supply has done something to offset the decrease. There seems little doubt that the comparatively large numbers of Bitterns still to be seen on very small areas of swamp must be due to the abundant food supply furnished by the introduced Australian frog which now forms a very large part of the bird’s diet. Native fish and small eels are also eaten, and the Bittern has no scruples also about taking the young of other water-fowl when it gets the chance. \ Like practically all native birds, it is included in the list of protected species, and is at present not in any danger of molestation except from irresponsible shooters and some few anglers who labour under a delusion that trout can be most easily lured with an artificial fly made from Bittern feathers, or “Matuku” feathers as they are called in this connection.

There is also some danger that inexperienced people may mistake the Bittern for the Harrier Hawk. It is about the same colour and size, and, when it rises with heavy flight and its neck drawn in, is not unlike a hawk at first glance. The nesting season begins about September and is a fairly long one, as nests are sometimes still being made in December. They are substantial rafts of sticks and broken rushes, always well hidden in the surrounding vegetation. Indeed, a Bittern sitting closely on its nest has a very good chance of escaping detection. The eggs are a very pale greenish colour, almost white, and five is the number most usually laid. If they escape the attention of passing Hawks or prowling Pukekos, all the eggs are usually hatched and the five chicks sprawl rather helplessly on the nest at first, protected by one of the parents while the other brings the large quantity of food necessary for their nourishment. They are not quite as ugly as other nestlings of the heron family and have a fair covering of buffy down. Their throats are enormous and of great elasticity, and each chick can, without difficulty, swallow the frog or other morsel almost as large as itself, which suggests that the rest of the body is just as elastic as the throat.

As they grow older they develop defensive habits and look most ferocious as they spread their half-sprouted wings and glare defiance. When fairly well feathered, but still unable to fly, they adopt other means of protection by leaving the nest when danger threatens and hiding themselves in the surrounding rushes. If the water is deep enough they will even slide entirely out of sight, gripping the base of the reeds with their feet and leaving only the tip of the bill exposed above the water. Still later, when they have left the nest finally, they use similar devices for protection, as well as adopting the frozen attitude so characteristic of adults.

The deep-throated boom of the Bittern is heard generally only in the spring. At other times the bird is silent except for an occasional croak of alarm or annoyance uttered when on the wing. •