THE NATURALIST.

Otago Witness, Issue 1901, 17 July 1890, Page 41

THE NATURALIST.

' The Swallow.

Some days before swallows le&ve us they assemble together, usually beside a river, where they wait for fresh arrivals, till a flock of many thousands is collected. Did we not know that similar gatherings were going on in many other. places, we could well imagine that every swallow in the kingdom waa in this particular spot. At Rotherham, in 1816, it was firmly believed that this was the case. Early in September a wonderful assemblage of the birds commenced ; their numbers kept on increasing day by day, until myriads upon myriads of them were collected. They roosted in willows, and at about 6 o'clock every morning rose from these in four, five, or six great divisions, each of which flew off, taking a different route from the rest, not only, it was supposed, in order that they might be distributed equally to search for food, bat also to gather in any stragglers that they might encoun ter. In the evening they would return from every quarter of the compass, reaching the willows some as early as 5 o'clock ; some not until the sun had set. This went on until the 7th of October, when the whole vast army rose in one mass and winged its way south. Probably they would have left sooner, but for some days previous to their departure there had been a contrary wind; and as soon as this changed they took advantage of it and went. The winter retreat of swallows has been a subject that has attracted attention in all ages. It has been supposed by some that on the approach of cold weather they retire to the inmost recesses of rocks, mountains, or decayed trees, and there lie torpid until the return of spring rouses them to active life again. There is just enough foundation for this idea to us to understand its prevalence in former times. Solitary swallows have been observed long* after their fellows have left our shores ; and again, a few birds sometimes appear long before the regular immigration has commenced. These are no doubt members of second broods, which were batched so late in the season that they had not sufficient strength of wing to fly off with their fellows. They lie torpid in some sheltered spot, and an unusually warm, bright day in late autumn or early spring will brirg them* out. Several have bsen found together nestling under the thatch in a barn; and it is these isolated cases which led men to believe that all swallows remained with us in a torpid state through the winter. Gilbert White was a supporter of this theory. He says that swallows "do not depart from this island, but lay themselves up in holes and caverns ; and do, insect-like and bat-like, come forth at mild times, and then retire again to their • latebrae.' " A far more extraordinary hypothesis than this is that of the " subaqueous hybernation " of these birds during the winter. It is difficult to understand how any but the most ignorant persons could bring themselves to believe in such an absolutely impossible idea. And yet many naturalists have given it their support; amongst them Klein and Linnssus. Indeed, the belief that swallows pass the winter at the bottom of ponds or rivers is still prevalent in some out-of-the-way parts of England. In support of the theory, Bishop Stanley, in his " History of Birds," mentions the following fact : — " On the 2nd of November, 1829, at Loch Ranza, in the island of Arran, a man, whilst digging in a place where a pond had been drained off, discovered two swallows in a state of torpor. On placing them near a fire they recovered." It is most likely that these birds had been left behiDd, and had found their way into some partially concealed hole after the pond was drained. Most latter-day writers on birds treat the idea of hybernation under water as being too extravagant to need serious refutation. The Rev. Mr Fleming, however, brings forward several unanswerable arguments to disprove it. He says that swallows are much lighter than water, and could not, therefore, sink in clusters as they are represented to do; and asks, if their feathers are previously wetted to destroy their buoyant power, in what manner can they resist the decomposing effect of six months' maceration in water, and apprar in spring as fresh and glossy as those of other birds ?

As a matter of fact, the majority of the KWiillows which flit over British streams and meadows during the warmer months, wing their way to Africa when the shortening days and chilly nights warn them that it is time to seek some more genial clime. A few swallows winter in the oases which are scattered about the northern edge ot the Great Desert ; but the main body of migrants from the shores of the British Islands txtood i heir journey considerably beyond this poiat. At Sierra Leone and on the River .Senegal swallows abound at all seasops of the year;

but from May to Ootober they are far lees plentiful there, showing that a large contingent of them has flown northwards. Mr Yarrell tells us that in January and February swallows are to be seen on the West Coast of Africa as far south as the island of St. Thomas, on the Equator. Natal becomes alive with these birds in November, and is deserted by them again in March and April. After Africa the favourite winter resort of swallows seems to be the north-west provinces of India, where they are found in considerable numbers during the months in which fog and frost reign over the British Isles.— All the Year Eound.

Thrush and Blackbird Hybrids.— ls it possible or probable that a cock blackbird should, in a wild state, pair with a hen thrush 1 My reason for asking the question is, that the year before last we had a perfect plague of blackbirds in the gardens here. Last year, the day before I went abroad, I went round the place with my gardener and destroyed all the blackbirds' nests we could find. As I was coming into the house I saw what I took to be—and believed was— a hen thrush sitting close. The gardener tells me a cock blackbird fed the sitting bird and the four young ones till they flew. • The man has been many years in my employment, and I think well worthy of belief. On Thursday last he called my attention to a cock blackbird and, apparently, a hen thrash just about the same bush, about 20yds from my smok-ing-room window, where the nest was last year. The birds were evidently paired, from their movements. We do not like to look at present for the nest, for fear of scaring them, but I will have them carefully watched, and, if they hatch, try and save the young ones. Would you kindly say if you ever knew of a case of the kind ? I shall have great pleasure in sending you the young if hatched this year. My little son pulled down the nest last year after the birds had flown, so I cannot say what it was like inside — a blackbird's or a thrush's. — M. M. (Oakley Park, Oelbridge, Co. Kildare). [The blackbird undoubtedly breeds occasionally with the song thrush, and in one case on record, which was published in the Magazine of Natural History, vol. vii, hybrids were produced from such a union for two successive years. — Ed.]— Field.