GARDEN NESTS.
IT has probably occurred to many owners of gardens to take year by year a census of their birds' nests. A census of this kind is interesting, not merely for purposes of comparison of one year with another, but because it leads to the keeping of records of all kinds of odd and unusual circum- stances connected with birds and their habits in the breeding season. It is pleasant to notice whether the migrant birds return at the usual season and in the usual numbers ; there is a fascination in trying to attract rare or shy birds to nest in a particular area of ground; and, as regards noticing the habits of individual birds, there is always the chance of being able to add a new fact to the chronicles of natural history. Indeed, it might be possible, if a sufficient number of owners of gardens were engaged in the pursuit of facts, to put together a really valuable report on the present position of a good many birds as regards increase or decrease in numbers, habits of feeding, and so on. Owners of gardens are selected from other country dwellers because each owner would be responsible for a specified area of ground, and there would be no overlapping of reports, as there would be if a number of different persons made entries as to the birds, say, of a large common or wood. And the probability would be that the returns from the gardens would be in the same proportion as the returns, could they be completed, from the whole of a given area. Suppose, for example, that in a particular parish there were a dozen members of a club or society, all of whom at the end of the season were to send in returns from their own gardens, varying in size, perhaps, from fifteen or twenty acres to an acre, the probability would be that the figures obtained would be proportionate to the size of the parish as a whole. There would be certain exceptions, of course, as in the case of rookeries or heronries or large ponds, which might not happen to be in the areas searched by the garden-owners. But you would get at some interesting figures as regards the numbers in any given year of such migrant birds as swallows, martins, and swifts, which make their nests in or on buildings; and there would be some valuable data on such points as the numbers of broods reared as compared with broods destroyed or nests deserted. This information would increase year by year in volume and so in value. More and more people become attracted year by year to the study of birds and their ways, and the more information that was collected, the nearer we should get to right conclusions on general questions—for instance, changes of habits among such birds as starlings— and on small but interesting points such as the building of supernumerary nests by wrens.
Statistics of this kind, gathered from wide areas over long spaces of time, would provide, perhaps, the best means that could be got together in a lifetime for studying so huge a question as evolution. A process extended through millions of years can only be reasoned about as a whole by deduction and inference ; but we may at least guess that the first steps towards evolution of species would have been departures from type which might have been observed on the spot had there been chroniclers to observe them. And even in our own time there have been examples of divergence from type which, if they had been noted year after year, might have formed link
after link in a long chain of evidence. The old name of "chimney swallow," for instance, which we do not bear
nowadays, would seem to point to the fact that at one time swallows built in chimneys, possibly because chimneys approached in shape to the hollow trunks of trees or holes in rocks, in which they had been accustomed to make their nests. From that possibility you may go on to speculate whether the spots on swallows eggs have come there as the result of the birds nesting more and more in the open, since swallows now
snake their nests on beams and ledges, open at the top, while their relations, the martins, which make their nests under eaves, and the sandmartins, which nest in holes and tunnels, have white eggs. Or take the case of starlings, birds which everywhere have proved themselves most adaptable in habits to changing circumstances. Starlings may nest in holes intrees, or in thatch, or sometimes in the under part of a rook's nest, 'which looks like a possible gradual transition from hole to tree. Here again you get an interesting point as to colour, for starlings' eggs vary from hedge-sparrow blue to blue so pale that it is almost white : the suggestion would seem to be that blue is the colour towards which the egg tends to change as a consequence of the bird coming, so to speak, out into the open. Pigeons suggest other points in the same problem. Some pigeons—stockdoves, for example—still nest in holes, rabbit burrows, or hollows in the stumps or " stocks " of trees. Other pigeons, such as ring-doves, lay in nests which are open to the sky, but all pigeons lay white eggs ; will there, then, come a time when pigeons will begin occasionally to lay bluish eggs, and so vary from the white archetype ; and will starlings in the same way begin to lay eggs which are slightly spotted, like song thrushes', and so come gradually through to eggs which are of a safer colour, like the mottled eggs of snissel thrushes, blackbirds, rooks, crows, magpies, and jays P Here is obviously a point where the slightest divergences from type, chronicled from time to time over a long period, might supply the most valuable data for the naturalist. Side by side with notes as to the colour of eggs, which vary in many species to a degree only to be realized by the examination of large collections, might come data as to possible changes of preference for this or that locality for a nest. Look, for instance, at the robin. Probably the commonest place in which to find a robin's nest is a hole in a bank or wall. But here and there one seems to meet little colonies of robins which prefer other places to banks and walla. In a particular area of ground in which the writer found a large quantity of nests last year, there were a number of banks which offered what looked like ideal places for robins' nests. But only one robin nested in a bank, and all the others, six in number, nested on the ground in the grass under some medium-sized larch trees. Except for the trees above them, the situation chosen was exactly that of a lark's neat. The single robin which nested in the bank also dis- tinguished itself from the others by doing what wrens do, and building a supernumerary nest which it did not use. The odd point about this nest was that it was placed immediately adjoining the nest in which the eggs were laid and the young birds reared, so that the two nests sat in the bank in the shape of a figure of eight—a sort of bed-room and dressing-room. This year no robin has built as yet, but a wren has already set up a fresh record for itself. It made a trial nest in the loose grass of a bank—one of the usual "cock nests," as they are called, some people holding that they are nests made by the cock in which to carry on his courtship. Then it chose one of a dozen little holly trees standing in a basket near a tool-shed, and began a "cock nest in that. The holly had to be moved, but it was planted in a hedge close by, and the wren duly finished the shell of the nest the next morning. A point to observe is that wrens are among the most particular birds about having their nests interfered with, and desert at once if the fabric is touched or loosened, as it might be in getting out an egg. Is it possible that these "cock nests" are made in such a frenzy of spring fever that the bird hardly notices interference or removal ? There would seem to be room here for further experiment.
Nests in gardens provide an opportunity which is not always possible elsewhere for calculating the chances of survival of the broods of different species, and a curious consideration occurs at once. If it is a fact that in the process of evolution birds are gradually leaving boles and coming out into the open, it is strange that the birds which nest in holes seem to lead, as a rule, safer existences than those which nest in the branches of trees or on the ground. Perhaps an artificial nesting-box does not provide proper premises for a scientific conclusion, but in the writer's experience it rarely happens that a tit nesting in the hole of a tree or a bird-box fails to bring off its brood. Thrushes and blackbirds nesting in hedges, on the other hand, and robins nesting on the ground must regard it as an exceptionally lucky thing to bring up a family, rather than
a terrible misfortune to lose eggs or young birds. Of the seven robins whose nests the writer watched last year, all of them in a small area of wood and garden, none of those which nested on the ground brought off a brood ; the only bird which reared a family was the robin which nested in the bank, and in the bank there were rats. The thrushes and blackbirds were not much more lucky than the robins. This year the first missel thrushes' nest has been robbed by jays; the hen was sitting comfortably enough one morning, and on the next five jays suddenly clattered up out of a neighbouring cabbage-bed, where lay the remains of the eggs. The missel thrushes are now building again, and if the nest, as seems likely enough, is robbed again, there will be a melancholy interest in the result. How many times will different birds start a fresh nest ? That is just one of the points which observers ia gardens can determine better than other people.
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