Notes on the Breeding Biology of the Buzzard
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Notes on the breeding biology of the Buzzard Geoffrey Fryer uring the 1970s and up to 1985, I made casual observations on the D breeding behaviour of the Buzzard Buteo buteo. Most of these were in the southern part of the Lake District, Cumbria, but others made elsewhere during the same period are also referred to here. Although various aspects of the breeding behaviour of the Buzzard are well documented (e.g. Melde 1971; Picozzi & Weir 1974; Tubbs 1974; Cramp & Simmons 1980), my observations revealed several apparently little-known or undescribed facets. Nest-site marking by crag nesters The habit of'decorating' the nest with fresh sprays of green leaves is well known, but some generalised statements are not always factually correct and its significance is still subject to debate. The repairing and maintaining of old nests in seasons when they are not in use is also well known. What seems not to be recorded is that actual sites, at least crag sites, may be marked by depositing green material there, even though no nest is constructed. In 1971, a pair of Buzzards nested on a crag in a Lakeland valley and raised one chick. This site was not used from 1972 to 1975, but, apart from noting the fact, I paid no attention to the nest ledge save recording that, on 26th April 1974, the nest was 'a wreck and not repaired at all'. On 21st April 1976, however, several shoots of holly Ilex aquifolium had been placed on the site. No attempt had been made to rebuild the nest, of which no more than a few old sticks persisted on the ledge. On 15th May, I found that, while one or two sticks had apparently been brought, no attempt had been made at nest rebuilding, yet several sprays of rowan Sorbus aucuparia had been placed on the site. On 22nd April 1977, no nest building had taken place, but two fresh green sprays of holly and one faded spray that had clearly been there longer were present; on 21st May, no additional material was present. On 23rd April 1978, on which date occupancy of another site within this territory was confirmed, two or three stalks of heather Calluna vulgaris had been brought and a few green holly shoots placed on the site. By 13th May, at least one further holly spray had been added, this despite a nest elsewhere in the territory having been occupied continuously since the first shoots were noted. This hints at the male being the bringer of the greenery, the female being usually otherwise'engaged at this stage of breeding. Males certainly bring green sprays to occupied nests, although MacNally (1962) saw only the female do so during the post-hatching phase at a Scottish nest. On 18th April 1979, a first, very rough attempt at remaking this nest had begun, and fresh 18 [fin/. Birds 79: 18-28, January 1986] Breeding biology of the Buzzard 19 holly shoots (not an integral part of the structure) were again present. On 6th May, the nest was complete and contained what proved to be the full clutch of two eggs. The same ledge was thus re-used after seven years of disuse, though not complete abandonment. The position of the nest was virtually identical on each occasion. These observations show, incidentally, how quickly Buzzards can make a nest: not always is it completed 'long before they lay their eggs' (Bannerman 1956). The marking of incomplete or vestigial nests with greenery and the phenomenon of nests being completed but not used had already been observed at alternative sites in this same valley. A well-fashioned nest found in 1970 was visited by a Buzzard which, however, used an alternative site. On 13th May 1971, the unused 1970 nest, although incomplete, was marked by three sprays of rowan which had obviously not long been in position. It was not used in 1972 and 1973 (no details kept of its condition). In 1974, it received some attention, but was not lined; on 29th March, however, several holly sprays were present, the nearest source being about 500 m distant, and on 26th April sprays of fresh rowan had been added. On 25th April 1975, sprays of holly were present, and on 20th May the nest had been made up and the female was brooding two eggs; one young was eventually reared. On 28th March 1976, two fern fronds (species not ascertained) lay on the unrepaired remains of this nest. On 21st April, these had withered, but no further green material had been added, nor was any found in 1977-85, and, following desultory repairs in 1977, the site appears to have been abandoned. On 30th April 1983, a visit to a crag to which one of a pair of circling Buzzards had been seen to plunge directly and steeply some two weeks previously revealed a newly constructed, but incomplete, unlined, nest. Lying on it was a tuft of great wood-rush Luzula sylvatka, partly green, partly brown; two heather tufts, one greener than the other; and a green spike of whorled leaves, seen only through binoculars, possibly of fir clubmoss Lycopodiwn selago. Very little of the heather in the vicinity was green at this time in a late season, and the tufts present must have been assiduously sought. On 25th May 1977, sprays of rowan were also found at a derelict nest visited by a Buzzard elsewhere in this valley, but such behaviour was not confined to one area. In an entirely different part of the Lake District, a nest used in 1973 (not examined in 1974) showed no sign of being remade on 26th April 1975, but a few fronds of polypody Polypodium vulgare had been placed at its centre. Particularly gratifying was a visit made on 29th April 1977, specifically to check this behaviour, to a crag site in a different Lakeland Valley where Buzzards reared two young in 1974, but which was known to have been unoccupied in 1975 and 1976. There, although some attention had possibly been paid to the sticks still present, no real attempt at nest making had been made, but three fresh sprays of holly had been placed on the ledge; these, but no additional green material, were still present on 20th May. A nest in a yet different valley produced one young from a single egg in 1982; in 1983, it retained much of its shape but was unrepaired, though a freshly severed spray of juniper Juniperus communis had been placed at its centre by 4th May, on which date the pair was occupying an adjacent, newly built, nest containing two eggs. By 29th April 1984, the same nest, still in good shape but unrepaired, had been marked by three separate sprays of juniper and a dead fern frond, and on 10th May 1985—by which date a few heather stalks had been added to the rim—the unlined nest cup again had a spray of juniper in its centre. Juniper grows nearby. In another valley, a nest which in 1981 failed at the egg stage was not used in 1982, but on 8th May four faded holly sprays and a wilted, but clearly more recently placed rowan branch with a stem at least 8 mm in diameter was present on the unrepaired nest, and several tufts of mat-grass Nardus stricta (see below) were also present. As this nest never became badly trampled, the latter could conceivably have persisted from the previous year, or could have been added with the green material. In a different valley, a nest discovered on 1st June 1985, to which some attention had probably been paid in that year, had a fresh frond of rowan at its centre and a similar, withered, frond at its rim. The placing of green material at nest sites or incomplete nests was established on a total of at least 22 separate occasions, involving nine sites and several seasons. The number of visits on which this was brought must have been greater: for example, the four holly sprays at one site presumably involved four separate visits (not necessarily on the same day). That fresh greenery, sometimes unaccompanied by faded material, was seen on dates 20 Breeding biology of the Buzzard ranging from 28th March to 1st June also hints at the possibility of renewal. Conclusive proof of the placing of greenery leading ultimately to nest making and egg laying, sometimes in subsequent years, was obtained at some sites. Equally conclusive proof of green material being placed on a previously used site that could not be used that year was also obtained, such material certainly being deposited at one site after nesting had begun elsewhere in the territory. Nevertheless, site-marking is by no means invariably practised. The first-mentioned site remained unused from 1980 to 1985, but no marking was observed. That the birds were aware of the site can hardly be doubted: a Buzzard was seen perched close to it early in the 1981 breeding season, leading me to suspect either nesting or at least marking, though neither occurred and no physical attention was paid to the site. I have seen a fern frond on an unrepaired tree nest used in the previous season—a parallel to the marking of crag sites—but in trees such marking is possible only when a remnant of an old nest survives. I can find no reference to the use of green material on what are sometimes nestless crag sites, but Blezard (1933) noted that 'the earliest sign of activity sometimes is a leafy spray placed on an old nest'.