LOCAL MIGRATION

New Zealand Herald, Volume LXXIV, Issue 22777, 10 July 1937, Page 10 (Supplement)

LOCAL MIGRATION

HAVING noticed some regularity in the times of arrival and departure of woodpigeons from his district each year, a correspondent has asked if the birds could be classed as migratory. NO LONG FLIGHTS Such regular movements can bo termed local migration. The native pigeon does not fly overseas. Whatever their ancestors may have done in the way of lout: flights, the various fruitpigeons of the Pacific region are now more sedenta-y a he' local in distribution, inhabiting small islands, or restricted areas on the Australian continent. The group to which the handsome New Zealand bird belongs includes a species once found at Norfolk Island and now extinct, another still found in small numbers at the ('hatham Islands, and the well-known New Zealand mainland bird CHANGE OF DIET Local migration can to some extent be explained by the need for a more varied diet than one district can supply, or by the fact that the kind of food suitable for older birds does noj; always suit the requirements of the young while still on the nest. Mr. A. J. Cameron, writing of observations made at Mangapeehi, states that there is

a noticeable increase in the number of pigeons seen there in April, at which time the birds are in poor condition. They feed on the fruit of tawa and maire until the miro berries are ripe, and rapidly attain good condition by the middle of winter. The majority seem to disappear in August and the} do not again appear plentifully until the following April. It should be noted that the period of apparent absence coincides with the times of nesting and moulting, and it would need careful investigation to determine whether or not they were really present in tho district, for nesting and moulting birds are not conspicuous, if the observer is sure that they are not present the only conclusion is that the birds frequent more suitable nesting areas elsewhere IN SUBURBAN GARDENS There is no doubt that pigeons in present-day New Zealand need to travel longer distances than in the past to find sufficient suitable winter food. Small isolated patches of bush are visited, and occasionally even suburban and city gardens. I do not, know of any food that can be provided to tempt them to prolong their stay under such circumstances; if the property owner wishes them to stay about, all that can be done is to refrain from molesting them when they set about stripping leaves as they will on laburnum and some other shrubs. STARLINGS AND FINCHES Conspicuous local migratory movements aro those of starlings, some of tho finches, and yellowhammers. The white-eye is another winter wanderer, readily tempted at this time of year to linger over pieces of suet, fruit, or any sweetoncd liquid. For tho most part their busy flocks are this month swarming over the lower and warmer coastal districts, but 1 have lately seen numbers in high-country beech forest, not far from the snow-line, feeding on the beads of honey-dew exuded by an insect embedded in the black fungus

Winter Movements of Birds Specially Written for The New Zealand Herald by R. A. FALLA, M.A.

which covers the trunks of the trees In tli'« delectable pursuit they did noi have the field to themselves, but wen in coin petition with a few bellbirds ant I several house sparrows.

WHITE-EYES FROM AUSTRALIA It is interesting to speculate whether regular local migration ever extends until it becomes an overseas migration, but we have not much information bearing on the problem. All we kitow is that active local migrants sporadically overflow the bounds of their native region and take up residence in a new one. This has occurred with the arrival of white-eyes from Australia within the last century, and probably with other species before that. The white-eye has not, however, therefore become a regular migrant between this country and Australia; rather, a section of the species lias become resident here, developed its new local migratory movements, and again overflowed to sub-antarctic islands further south. Among imported birds the starling and the redpoll have done the same, both having reached Macquarie island. FLIGHTS AT NIGHT Sometimes a local migratory movement is performed with the same concerted and definite movement of flocks that characterises the behaviour of overseas migrants. When such flights take place at night the birds can often be heard calling, and the notes dis-

tinguished in the case of white-eyes, stilts, terns and some others. Stilts, which nest in summer in the South island seem to perform a winter migration to the North Island, returning generally in July. This year, Mr. E. F. Stead has informed me that a small flock had already made its appearance on Lake Ellesmere, Canterbury, at the end of June. There are apparently other stilts that do not leave the North Island at all, but both nest and winter there. NIGHTINGALES AND SWALLOWS Although so many imported birds have settled down to a fairly regular habit of local migration, it is to be noted that long-distance migrants from Europe, when brought to New Zealand and released, have not established themselves here either as residents or as migrants. Nightingales, swallows, and other well-known species have been tried repeatedly without success. It is evident that the double difficulty of beoomine established in a new home and of finding suitable outlet for migratory impulse as welhhas proved too much for them. EARLY NESTING An interesting commentary on the longer breeding season enjoyed here by European birds whose ancestors were developed under more rigorous climatic conditions is contained in a letter from Mr. E. 1). I'ritehard, of AVaimamaku, Hokianga, written on June 21. A week before that date he had watched a song thrush gathering cut grass from a heap and carrying it to an Escallonia hedge, where it had already commenced to build a nest. Such an early start must mean a very long breeding season, and it helps to explain the numerical advantage which so many introduced birds show over tho native species, few of which begin nesting before August. I do not know of any case where marked thrushes hp ve been observed through a breeding season, but consider it likely that they might rear four broods.