Studies of West Palearctic Birds 197

Studies of West Palearctic birds 197. Tree Sparrow J. Denis Summers-Smith ABSTRACT The Tree Sparrow Passer montanus and the House Sparrow P. domestkus are the only two members of the genus Passer that breed in Britain & Ireland. They are an interesting pair of congeners: both have extensive distributions in the Palearctic and Oriental Regions; both are commensals of Man in at least parts of their ranges; and both, despite some recent decreases in numbers in areas where they have long been established, are still expanding their ranges. A recent article in this series concentrated on the House Sparrow (Summers-Smith 1994); we now turn to the less familiar of the British pair, the Tree Sparrow. It is an odd comment on human nature that most British birdwatchers, having ticked off the House Sparrow on 1st January for their annual list, scarcely give the species another look; yet the Tree Sparrow is generally regarded with great affection and faithfully recorded throughout the year. I do not think that this is solely because the Tree Sparrow tends to be regarded as something of a rarity in Britain; there is something appealing about it that makes it particularly attractive to those interested in birds. The fact that the Tree Sparrow is a frequent subject in Oriental painting, going back as far as the twelfth century, may perhaps reflect something of this appeal. The simple brush strokes of the Chinese and Japanese styles of painting show an obvious familiarity with the bird and its behaviour. There may, however, be another side to the fascination in the East. The Tree 124 [Brit. Birds 91: 124-138, April 1998] CO British Birds Ltd 1998 British Birds, vol. 91, no. 4, April 1998 125 Sparrow is widely eaten in China, where it is known as the 'hemp bird'. 'The hemp bird is rated as the most sensuous of birds; and so, eating its flesh is supposed to increase sexual potency' (Eberhard 1986). Could it be that the birds' addiction to hemp Cannabis does something for the eater? In contrast, the Tree Sparrow does not seem to have exercised the same attraction for painters in the West. It is, however, currently attracting much attention for a different reason: among declines in the numbers of birds in agricultural areas, the Tree Sparrow headed the list of ten of the most familiar farmland species with a significant fall in population in Britain in the last 25 years (BTO News 199, July-August 1995). In this article, I shall concentrate on those aspects of the Tree Sparrow's life that have particularly fascinated me: its origin; recent changes in its distribution and numbers—decreases in numbers in much of Western Europe, contrasting with an expansion in range to the south in both the Far East and southwestern Europe; and the relationship between it and the House Sparrow. Identification The Tree Sparrow is unusual among sparrows in that the female has adopted 'male-type' plumage, with a patterned head and black bib, so that the sexes are indistinguishable in the field. Tree Sparrows are superficially like male House Sparrows, but can readily be recognised by their sleeker, neater appearance and a distinctive white semi-collar that is very obvious, even at a distance. The call is also quite distinctive: it is softer and higher-pitched than that of the House Sparrow. To me it sounds like a monosyllabic 'chirp' (though sonagrams show that it is, in fact, disyllabic) compared with the deeper, more obviously disyllabic 'chirrup' of its congener (Cramp & Perrins 1994). Origins The finches (Fringillidae), buntings (Emberizidae) and weavers (Ploceidae) have long been recognised as the major seed-eating families of birds. Linnaeus included the sparrows in the finches, but during the last century opinion has changed and most authorities now place them with the weavers (though not without some dissent), mainly on the grounds of the similarities in their nest-building activities. Anyone who has compared the nest-building skills of the weavers with the activities resulting in the domed, but otherwise untidy structures of the sparrows, will be excused any failure to see any close similarity. The current opinion, to which I subscribe, is that the sparrows are best considered as a separate family, Passeridae; included in this family are the snowfinches Montifringilla and the rock sparrows/petronias Petronia. The Passeridae differ from the other seed-eating passerines in their technique of dehusking seeds. They specialise particularly on the seeds of the larger grasses. I have hypothesised that the genus Passer most probably had an Afrotropical origin, with a pioneering group spreading up the Rift Valley in the Pliocene, 126 Summers-Smith: Studies of Tree Sparrow reaching the Levant 500,000 years ago. These birds spread widely over the Palearctic and Oriental Regions, but were subsequently separated into nine isolated populations during the Pleistocene glaciations. The next major factor in the history of the northern sparrows was the transition of Man from a hunter-gatherer to a sedentary agriculturist at the end of the Pleistocene about 10,000 years ago. The sparrows, preadapted to the seeds of the grasses that were the precursors of the cultivated cereals (wheat, barley, rice), were prime candidates to exploit the situation. Of the 20 species of sparrow currently extant (25 according to some taxonomists), no fewer than 60% (12 or 15 respectively) show some association with Man, nesting in buildings, and feeding on cereal crops, scraps around houses and feed put out for domestic animals. The two populations best placed for this were the birds living in the Fertile Crescent of the Middle East and the Yellow River Valley in present-day China, the centres where agriculture originated: the putative ancestors of the House Sparrow and Tree Sparrow respectively. Both of these became in fact 'house sparrows', anthropophiles or commensals of Man. Range Both species spread from their centres of origin with the advance of agriculture, and today have extensive and largely overlapping distributions over much of the Palearctic and Oriental Regions. The Tree Sparrow ranges from Japan and China to the western seaboard of Europe. In the north, the distribution is similar to that of the House Sparrow, reaching about 60°N, sometimes even farther; Brayton Holt informed me (in litt.) that Tree Sparrows visited his camp at 76°N in the Taymyr peninsula in July 1994, though these were presumably wandering rather than breeding birds. In the south, it is present throughout Indochina, Thailand and Burma, but farther west the southern limit does not go south of the Himalayas, the Afghan plateau and the Elburz Mountains of Iran. It is absent from the Indian peninsula, Iran south of the Elburz, and the Middle East, but it extends into Turkey and much of southern Europe, though it is somewhat sparsely distributed in Greece and the Iberian peninsula. It is not known when the Tree Sparrow first arrived in Britain & Ireland— the earliest record that I can find is for Scotland (Sibbald 1684), oddly preceding that for England: a bird collected in Yorkshire in May 1720 (Nelson 1907). Of course, this may have been the result of difficulties in separating the species from the House Sparrow rather than evidence that it was absent, though the great English naturalists Ray and Willughby (Ray 1678) had already recognised it as a separate species in the seventeenth century. It is remarkable that, although the House Sparrow had probably been in England since Roman times, it was the Tree Sparrow that was present in the Western Isles and the adjoining west coast of Scotland from 1758 (St Kilda), though the House Sparrow began to colonise in the 1880s and the Tree Sparrow had disappeared by 1930. In Scotland, it is largely confined to the east coast and the lowlands (Baxter & Rintoul 1953; Thorn 1986). British Birds, vol. 91, no. 4, April 1998 127 A 32. Tree Sparrow Passer montanus with food for nestlings, Worcestershire, June 1983 (Af. C. IPiftes) The World range of the Tree Sparrow largely matches that of the House Sparrow, but with two major differences: the House Sparrow is missing from Japan, China, Indochina, Thailand and Malaysia, where the Tree Sparrow is a common bird of the built-up areas; whereas the Tree Sparrow does not occur in southern Asia from peninsular India to the Middle East and North Africa, where the House Sparrow is common. Why these large areas should be restricted to one of the two urban species, which coexist elsewhere in much of their ranges, poses an interesting question. Range extensions The second half of the nineteenth century saw a significant attempt by settlers from western Europe to introduce familiar birds from their original homelands. The House Sparrow was the most outstandingly successful of these; the Tree Sparrow, introduced in much smaller numbers, less so, though populations have become established in both Australia and North America. The species was first introduced to Melbourne, Australia, in 1863; the birds survived and after a slow start have recently shown a marked expansion and now occur over much of Victoria and southern New South Wales. In the USA, the colonisation has been less dramatic. Tree Sparrows were first brought to St Louis, Missouri, in 1870, before House Sparrows were present there. Following the arrival of the House Sparrow, the Tree Sparrows moved out into the farmland on the eastern side of the Mississippi and are now reasonably secure in the plains of the Mississippi and Illinois rivers in southern Illinois. 128 Summers-Smith: Studies of Tree Sparrow More interesting, however, are the recent extensions in southwest Europe and southeast Asia, where there is evidence that much of this has been a natural spread rather than a deliberate introduction by Man.

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