MUTTON BIRDS

Forest and Bird, Issue 58, 1 November 1940, Page 10

MUTTON BIRDS

(By Rosaline Redwood.)

THEIR ARDUOUS LIFE

IN September they thousands of duskywinged mutton-birds, flying in mass formation like a black cloud suspended between heaven and earth. From distant Northern Asiatic shores they make their graceful flight, covering an almost incredible distance, to New Zealand’s Mutton Bird Islands, a straggly, scattered formation of bush-clad islands lying off the coast of Stewart Island. When the long migratory trip is almost over and the islands come in sight, some uncanny instinct guides them to their old nesting ground, where year after year the same birds and their families nest. The flocks wheel and scream in winged excitement, and when each bird is above the right area of land it closes its dusky wings and simply drops to earth. This is certainly a strange method of landing. Some birds are killed by the fall, while the others lie for a moment as if stunned, then scuttle down their empty burrows. - It is stated that the birds know the burrows which they occupied the previous year, and these they commence to clean out, preparatory to laying. The burrows, which extend usually a few feet into the spongy ground of the islands, are so numerous that they fairly honeycomb the surface in many places. It may be necessary for the younger birds to make fresh burrows, but, whatever the case may be, both male and female birds share in the labour, working tirelessly without thought of food until the task is accomplished. Leaves of the muttonbird tree are used to line the nest. Following the mating season, each female lays its one large, white egg. The common belief is that all birds lay on the same day, the 25th November, but more recent investigations have proved that eggs are deposited during the

months of November, December and even later. When the young one is hatched the parents

leave before daybreak in search of food, returning after dusk. If by chance an adult bird is delayed in leaving in the

early hours, it will remain in its burrow all day rather than venture out in broad daylight. The birds leave their islands

in mass formation, fishing in flocks, sometimes many miles from land. It is fascinating to watch these dense black clouds of birds. The leaders of the flock swoop gracefully ahead of shoals of small fish, heading them off, and then diving commences. Although the muttonbird is practically helpless on land, it is a strong swimmer and fast flier, and small fish fall an easy prey to its sharp beak. All day the birds gorge on fish, and at dusk bear down on their home islands again, the noise of thousands of wings being deafening. There is great excitement in the burrows. The young one pushes its beak inside that of the parent, and the partly digested bits of fish on which the parent has been feeding all day are vomited up. On this fare the young one soon becomes very fat, and by April is often larger and fatter than its parents. In appearance it resembles a soft grey fluffy ball. However, the Maori mutton-birders, who commence their annual killing season in April, are not deceived by the young bird’s apparent softness, for they wear protection on their hands and arms before reaching into the burrows. The bird has a sharp beak and can also use its feet to advantage, and as the scratches it inflicts often fester badly, the natives take necessary precautions. About May some of the old birds leave, but a few always remain behind for another month or so to guide the numerous young ones which escape the mutton-birders, back to the place whither they and their ancestors have gone for

centuries. In the meantime the young birds are gathering strength for their first long flight. The oil which is secreted in their crops becomes stronger, and is the main source of nourishment on which they must rely. With the parents gone and no food supply available, the chicks live on their store of fat. They become thinner and more vigorous, and adult plumage appears. At night they flop out of their burrows and test their wings awkwardly, flapping them aimlessly. And then the great day arrives when they congregate on suitable ledges of rocks from which they are able to leave with ease, and the first flight lasts until the young wings are tired, when the bird comes to rest on the water. After

a short spell off it goes again, this time for a longer flight— so on until it reaches its distant destination. The mollymawk and other vultures of the deep know exactly when the mutton-birds will leave their islands, and they come from far and wide to gather in the locality of the MuttonBird Islands, there to wait for the prey that is theirs. Many birds are drowned - each year, and some are blown out of their course by strong winds and left to perish, but it is certain from the number that return that most of them reach their migratory land safely.

Such is the arduous life of one of the most fascinating and remarkable of New Zealand’s migratory birds.