Sunday, December 17, 2000		Nature

THE name mormon was accorded to blue wrens because it was believed that the males maintained harems of a number of females. The reason for the belief is that the bright blue males are often seen with a group of brown birds, wrongly thought to be females. Recent studies have shown that these brown birds in the winter groups are actually young birds from the previous breeding season who remain with their parents. They are not adult females as was believed earlier. In these birds young ones out of the nest show brown plumage patterns like their mothers in their initial stage. For the first six months after emerging from eggs both male and female youngsters look alike and are almost impossible to fell apart. When winters come the male develops a blue tail which was earlier short and stubby and later moults into a full blue plumage. Their similarity with their mothers, perhaps, had led to the belief that males in these birds keep harems.

These birds are unique in the sense that unlike other birds their young do not leave their parents even after growing to adolescence and all the members live like a single social unit. Nesting in these birds takes place in spring and summer and during rest of the year whole family lives together, unlike other birds whose young leave their parents as soon as they are able to find food and shelter for themselves. When next spring comes and breeding pressure mounts, young females tend to leave their kin in search of a territory where males do not have partners. On the other hand, young males, who mature slightly later than their sisters, stay back with their parents, and even after fully maturing they do not leave their parents and instead lend a helping hand in nesting duties, e.g. feeding their younger siblings or even taking over the fledglings entirely, while their parents rear a second clutch.

Sometimes it happens that this togetherness of young male birds and their parents lasts for several years. During this time if anything happens to the father then a son take his place. In this way it is wrong to say that blue wren males keep several mates rather it is other way round.

In splendid fairy wren or splendid blue wren or banded wren, males have dazzling blue plumage while females are dull in colour. Apart from this, females are often in short supply because for reasons yet unknown they have a higher death rate than males. Consequently many males fail to find females so they stay at home and help in raising their younger brothers and sisters. But the fact is that these siblings may not be their real close relatives. A study which analysed the genes of these wrens found that the breeding male in a group is rarely the father of offspring he helps to rear. Instead, often the father of chicks is in a nearby nest. It seems that once he has plenty of helpers he loses interest in rearing offspring and goes off in search of extramarital relations, leaving his own female for other males.

Name ‘wren’ is given by Europeans to the various bird species throughout the world. Same is the case with Australian wrens. When the first white settlers came to Australia they were fascinated by the rich and unique wildlife of the country, but at the same time they also looked for similarities between its flora and fauna and that of England. In Europe, specially Great Britain, small birds with cocked-up tails are called wren, so the settlers named all the similar-looking birds in Australia wrens. Now there are a number of birds in that country with wren as part of their names, e.g. heathwren, grasswren, scrubwren, fieldwren, emuwren, and the best known among the group is blue wren, sometimes also called fairy wren.

Emuwrens are a group of birds which include a number of species. Their tail which has only six long filament-like feathers has earned them this name. Total length of the bird is 18 cm of which the tail accounts for 12 cm.

If we look at the tail feathers we will find that the delicate filament-like appearance of the feathers is due to a reduction in number of barbs and barbules. These birds have an attractive body plumage with shades of delicate blue around the throat and most of the remaining plumage is deep buff in colour.

There are about three species of emuwren found in different habitats of Australia. Some experts believe that all these birds belong to one species, and the different birds are simply races which have evolved to fit the ecological requirements of each particular habitat.