Population study of Buzzards in the New Forest during By C. R. Tubbs. Nature Conservancy, Shrubbs Hill Road, Lyndhurst, Hampshire

Transcription

1 British Birds Vol. 60 No. 0 OCTOBER 967 Population study of Buzzards in the New Forest during By C. R. Tubbs Nature Conservancy, Shrubbs Hill Road, Lyndhurst, Hampshire NTRODUCTON THE STUDY RERDED in this paper covered the five years from 962 to 966. ts main aims were to establish the size of the breeding population of Buzzards Buteo buteo in the New Forest, Hampshire, and to obtain information on breeding success and food. Ten addled eggs were taken (under licence) and analysed for residues of organochlorine pesticides. ETHODS Occupied nests were found (a) by examining all known formerly used nests each year and (b) by carrying out prolonged and repeated watches from vantage points overlooking the woodlands. The consistent attachment of pairs of Buzzards to paicular localities was taken as a guide to the location of nests and these areas searched. Where searches failed to reveal a nest, fuher observation was usually necessary (especially if several pairs were present in a relatively small area), in order to be ceain that the birds were additional to others whose nests had already been found. An estimated average of 360 man/hours per season was spent in observation alone; searches probably occupied a comparable time. STUDY AREA The study area, which is defined in fig., embraced all but a small pa of the common lands and Forestry Commission woodlands of the New Forest, together with intermixed and peripheral agricultural holdings. 38i

2 BRTSH BRDS FG.. ap of the New Forest, Hampshire, showing the area of Z.J square miles in which this population study of Buzzards Buteo buteo was made during the five years , with divisions into the broad habitat categories of (a) woodland, (b) heathland, acid grassland and valley bog (left white), and (c) agricultural and residential land. Also marked is the line of the legal perambulation which defines the boundaries of the New Forest {drawn by R. A. Fenton) t totalled 2.5 square miles, comprised of approximately 33,000 acres of woodland, 32,000 acres of heathland, acid grassland and valley bog, and almost 7,000 acres of agricultural and residential land. These three broad habitat categories are indicated in fig., from which it will be seen that the woodlands are mainly distributed in two large tracts, one extending roughly east to west across the study area and the other along its noh-east side, with smaller sections elsewhere. The greater pa of the woodland is statutory silvicultural enclosure, roughly half of which carries conifers. The remainder, about 7,000 acres, consists of unenclosed hardwoods, mainly beech Vagus and oak Quercus. HSTORCAL SURVEY oore (957) showed that, from being a common and widespread breeding bird in Britain at the beginning of the 9th century, the Buzzard suffered a general decline and a retraction of its range west- 382

3 BUZZARDS N THE NEW FOREST ward in the course of that century. By 900 it was confined to west and central Scotland, noh-west England, Wales, the south-western peninsula and an isolated outlier the New Forest. Between 95 and 954, however, the species had reoccupied much of its former range in southern and central England and eastern Scotland. oore correlated these distribution changes with intensified game preservation between 800 and 95 and with its subsequent decline. Fuher, he demonstrated an adverse correlation in 954 between the distribution of Buzzards and that of game preservation areas in Britain. Persecution by collectors he considered a secondary cause of the 9th century decline. The Crown lands of the New Forest, of which most of the present study area is comprised, were not subject to game preservation during the period of the Buzzard's general decline and it is probably mainly for this reason that an isolated breeding population survived there. Neveheless, the species undoubtedly suffered at the hands of collectors, actively assisted before 880 by the Crown Keepers. Until the 86o's the Buzzard appears to have remained numerous in the Forest. Wise (863) noted that it 'breeds in nearly all the old woods, but is becoming scarce'. The most intensive period of persecution appears to have occupied the following two decades. By 880, when the Hon. Gerald Lascelles was appointed Deputy Surveyor, egg and skin collecting was at its height. 'Everything in the shape of a bird of prey was... killed and if possible sold' by the Forest Keepers (Lascelles 95). Under Lascelles's administration there began a new policy of wildlife conservation a policy which he actively pursued until his retirement in 95. Neveheless, if the meagre records of eade- Waldo (900) and Kelsall and unn (905) are to be relied upon as a true picture, the breeding population of Buzzards at the turn of the century was small. Lascelles gave the impression that the population was substantial during the first decade or two of the present century, but that he was not prepared to divulge details. Thereafter, printed records were few and vague until the late 950's. The first published reference to a population figure was given by Cohen (963) who stated that 'J. B. Watson... estimated that about ten pairs were breeding in the New Forest in 940, and by the early 950's this figure had probably doubled'. The manuscript notes of B. J. Ringrose, covering the period 927 to 935, shed a somewhat different light on the species' status a few years earlier. Ringrose's notes related to the noh and west of the present study area and contained persistent references to pairs or nests at thieen sites in every year from 928 to 935. Of these sites, all but one carried nesting pairs during the present study and only two additional sites were recorded in the area by me, which suggests that the breeding popula- 383

4 BRTSH BRDS tion in the late 920's and early 930's was probably little different from that of today. f the memories of the older Forest Keepers are to be trusted, this picture held good for the Forest as a whole during the three decades preceding the spread of myxomatosis into the Forest in 954- The resulting decrease in Rabbits Oryctolagus cuniculus in 954 and 955 apparently had only a temporary effect on the numbers of Buzzards. According to Cohen (963), 'in 956 fewer (Buzzards) were repoed... and there was only one actual record of a successful brood. Three nests found in the Forest in April that year... had fresh greenery on them, but had been abandoned by ay'. According to the Forest Keepers, the numbers of adults remained normal, but fewer pairs bred. Population figures given in The Hampshire Bird Repo for the years immediately preceding the present study were 'probably 25 plus pairs with 8 definite sites and two known to have bred successfully' in 958; 34 pairs 'probably bred within the Forest boundary' in 959; 28 pairs 'known to have bred in the Forest, but none known to have reared more than one chick' in i960; and 35 pairs, '25 of which raised one young with very few known to have raised more' in 96. The area covered by these figures was not defined, but it presumably conformed to the legal perambulation (see fig. ). y own notes for 96 refer to an estimated 35 pairs within the survey area, of which eleven pairs each reared only one young and six reared two young. RESULTS Population si%e and breeding success The known breeding history of pairs of Buzzards at each of a total of 37 localities in the study area during the period is traced in the appendix on pages At 27 localities pairs were present in each year of the study period. A fuher four localities where pairs were present from 963 to 966 were not examined in the first year of the study. From two localities where pairs were present from 962 to 964, and from one where they were present in 962 and 963, Buzzards were subsequently absent. One pair was present in a new locality in 965 and breeding proved there the following year; one locality was used in 965 only; and another in 966 only. Table on page 386 summarises population and breeding data for each of the five years. Allowing for the four sites not investigated in 962, but occupied in the succeeding four years, this table suggests a static population of pairs of adults, giving a density of one pair to between 3.3 and 3.4 square miles. n addition, 'unattached' and presumably immature birds were present, although it was never 384

5 BUZZARDS N THE NEW FOREST possible to arrive at a total figure. Breeding data, or evidence suggesting non-breeding, was obtained for between half and three-quaers of the pairs recorded in each year of the study. The reference in table i to pairs which probably failed to lay eggs requires a little elaboration. n seven instances pairs were recorded as having either built new nests or rebuilt old nests without, however, laying eggs in them. Pairs of Buzzards are sometimes prone to 'patch up' more than one old nest in a season and, with this in mind, thorough searches were made for a second occupied nest in each of the seven localities. None was found, however, and the interest of the adults seemed to centre on the empty nest in each case. n the remaining eight records which appear in this last column of table i, thorough searches failed to reveal more than old, untouched nests and the behaviour of the birds suggested non-breeding. n dense and extensive woodland, however, nests can be missed and it was thus viually impossible to obtain absolute proof that breeding had not been attempted at nests which were never found. n fact, in view of the time spent in repeated searches and observation, and remembering the ease with which nests can often be found when the young are near the flying stage and very noisy, the balance of probability is in favour of a greater frequency of non-breeding, or unhatched clutches, than was recorded. Bearing this in mind, the data in table i on page 386 and in the appendix on pages permit the following four main conclusions to be drawn: (a) That there was a relatively high frequency of non-breeding, addled clutches and egg-breaking during the study period. (n no instance was there actual proof that the adult Buzzards were responsible for breakages.) The ratio of pairs which reared young, to pairs which laid clutches but reared no young, to pairs which probably failed to lay eggs is set out below, with information on nesting failures expressed as percentages ; 0 : 5 : : 2 :4 : :z 5::8 (0% clutches laid failed to hatch; 6.7% of total did not rear young) (6.3% clutches laid failed to hatch;.8% of total did not rear young) (25% clutches laid failed to hatch; 36.8% of total did not rear young) (5% clutches laid failed to hatch; 22.7% of total did not rear young) (6.3% clutches laid failed to hatch; 37% of total did not rear young) Whilst these figures suggest a sudden onset in infeility and nonbreeding during and after 964, it is likely that, as with the annual 385

6 BRTSH BRDS Table i. Summary of population and breeding success of Buzzards Buteo buteo in the study area in the New Forest, Hampshire, during Year Number of pairs present Successful Number of pairs breeding proved Young reared *5 24 Clutches failed to hatch or broken _ 4 3 Pairs probably failing to lay eggs increase in the number of pairs for which data were available, they were paly perhaps more a function of increasing efficiency of observation and increasing knowledge of the ground. n other words, with each year a larger number of old nests became known, increasing the chances of finding occupied nests without a search and releasing more time to concentrate observation and search on a progressively smaller number of pairs. The drop in the number of addled clutches but sharp rise in the number of apparent non-breeders in 966 might at first sight be taken as complementary and representative of a stage in a general decline in the breeding ability of the population. Of the nonbreeding pairs in 966, however, four had successfully reared young in the previous two or more seasons and only two had a history of hatching failure in the previous two years. (b) That non-breeding or failure to hatch eggs was not necessarily consistent at any one site for more than one or two years. Only one of the 37 pairs (the one at site 32*) had a history of non-breeding, hatching failure and egg-breaking for three years of the study. Of the four sites which were abandoned during the study period, birds were absent from two after, in one instance, one year and, in the other, two years of failure to breed. (c) That the average clutch size was less than two and that losses of eggs (through failure to hatch) and of young on successful nests were fairly high. Of the 33 clutches whose size was definitely known in 963, 964 and 965 the years for which this information is available nine were of a single egg, 2 of two eggs and three of three eggs, giving an average clutch size of.8. At 73 successful nests in the study period the average size of broods reared was.4 (44 broods of one and 29 of two). This seems to be a smaller average than in hill country fuher noh (H. ayer-gross in lift.). No broods of more than two young were recorded as reared during the study period. The cause of death of young on the nest was in no case satisfactorily explained, * Site numbers correspond to those given in the appendix on pages

7 BUZZARDS N THE NEW FOREST although in two instances they appeared very weak when inspected about a week before being found dead. (d) That there was no decline in the number of adult pairs present in the survey area during the five breeding seasons which were studied from 962 to 966. Location and persistence of use of nests At most of the 27 sites where pairs were consistently present during the study period, two or more different nests were known, although not all were necessarily used during the study period. n some cases these were separated by as much as half a mile, but they were normally less than 200 yards apa. At one site (23) a close group of no less than 4 nests was found, indicating a long history of use. ost nests at which pairs bred during the study period were not occupied in more than two consecutive years, although they were sometimes returned to after a year or two in which an alternative nest had been used. n fact, only four pairs used the same nest in more than two consecutive years at site 3 in 964, 965 and 966; at sites 7 and 9 in 962, 963 and 964; and at site 6 where the same nest was used in each of the five study years and had also been used in the three years immediately preceding this period. Nests were invariably situated either close to a substantial gap in the woodland canopy or near the woodland edge. ost were from 40 to 75 feet from the ground and in oak Quercus robur and Q. petraea or Scots pine Pinus sylvestris. At four sites, however, they were consistently in beech Fagus sjlvatica. n single instances Corsican pine P. nigra, Weymouth pine P. strobus, Douglas fir Pseudotsuga menyiessii and Norway spruce Picea abies were used, the last nest also being exceptionally low at only about 30 feet from the ground. Prey The prey species available in large quantities to Buzzards in the New Forest are birds of many species, Rabbits (which increased steadily in the area during the study period despite local outbreaks of myxomatosis), reptiles and Frogs Rana ridibunda. The Sho-tailed Vole icrotus agrestis, which Dare (957), for example, recorded as the main prey species in pa of Devon after the drastic reduction of the Rabbit by myxomatosis, occurs only locally, mainly on agricultural holdings. The Wood or Long-tailed Field ouse Apodemus sylvaticus, by far the commonest rodent in the woodland and heathland areas, is mainly nocturnal, although in fact this species was probably taken in some quantity. No regular source of carrion was available. Seventy-seven visits were made to 54 nests during the fledgling period. All prey remains found were recorded. The analysis in table 2 387

8 BRTSH BRDS Table 2. Prey remains found on 54 nests of Buzzards Buteo buleo in the New Forest, Hampshire, during Prey is listed in approximate order of frequency of occurrence during visits to nests Species Frequency of occurrence REGULAR Jackdaw Corpus momdula Jay Garrulus glandarius Stock Dove Columba oenas Blackbird Tardus merula Song Thrush Tardus pbilomehs Woodpigeon Columba palumbus Rabbit Oryctolagus ctmiculus Wood ouse Apodsmus syhaticus Feathers/remains on all 54 nests, often in great quantities Feathers/remains on 43 of the 54 nests, often in large quantities Feathers/remains on 3 nests ' Feathers/remains on 26 nests Feathers/remains on 2 nests Feathers/remains on 8 nests Often collectively in large quantities Remains on three nests 962; one nest 964; all eleven nests 965, in several cases in large quantities; on all nine nests 966 Remains on 23 nests RREGULAR Green Woodpecker Picus viridis Pheasant Phasianus colchkus Woodcock Scolopax rusticoln Sho-tailed Vole icrotus agrestis ole Talpa europaea Grey Squirrel Sciurus carolinensis Hare Lepus europaeus Grass Snake Nafrix natrix Tawny Owl Strix aluco Eight times on seven nests (adult remains five times, juvenile three times) Remains of chicks six times on five nests; primaries of adult once Remains of chicks five times on four nests; feathers of adult once Five times on two nests Four times on four nests (carcase untouched in each case) Four times on four nests Twice on two nests Twice on two nests Twice on two nests (juveniles) Chaffinch Fringilla coelebs Red-legged Paridge Ahctoris rufa eadow Pipit Antbus pratensis White domestic dove Columba sp. agpie Pica pica Starling Sturnus vulgaris Slow-worm Anguis fragilis Adder Vipera berus Once (adult) Once (chick) Once (juvenile) Once Once (juvenile) Once (adult) Once Once 388

9 BUZZARDS N THE NEW FOREST is, despite its obvious limitations, probably a fair reflection of the relative frequency with which the different prey species listed were taken. Remarkably few pellets were found. Thiy-one examined roughly in the field (from four nests in 962, three in 963, four in 964, five in 965 and one in 966) contained mainly the remains of Wood ice, insects (chiefly beetles) and Rabbit fur. t is interesting to note that no Frogs, lizards hacea spp. or shrews Sorex spp. were recorded from nests, although it is probable that they were taken. The analysis also masks the extent to which inveebrate prey was probably eaten. Neveheless, it seems likely that the bulk of Buzzard prey in the study area was comprised of medium-sized birds of various species, Rabbits, small rodents (mainly Wood ice) and reptiles. Kinging recoveries Table 3 summarises ringing and recovery data. A total of 57 young Buzzards was ringed in the survey area during the period. n addition, a brood of three was ringed in 957, of which two were subsequently recovered; for completeness these have been included in the table. The recoveries, though representing only a small propoion of the number ringed (one-twelfth or 8.3%), suggest a multi-directional dispersal of young birds in their first and second winters. No ringed Buzzards were seen at nests in the Forest during the study period, but little nest-observation was carried out. Table 3. Numbers of Buzzards Buteo buteo ringed in the New Forest, Hampshire, with details of those subsequently recovered, 957 and n"i957 only one brood of three was ringed and so the two recoveries in 958 and i960 were from the same brood; the other three recoveries were all from broods of one Year Number Ringing sites of Place, date and Distance and ringed ringed those recovered method of recovery direction site 33 Bosham, Sussex, 4th April 958 (dead 30 miles E three or four days) site 33 Poole, Dorset, about 9th February 25 miles WSW i960 (skeleton, long dead) site 3 La almaison, Aisne, France, 28th 270 miles ESE September 962 (killed in pole-trap) site 33 Rowlston, Hornsea, Yorkshire, 7th 25 miles NNE September 962 (dying) site 2 nkpen, Hungerford, Berkshire, Oct- 35 miles N ober 964 ('remains')

10 Table 4. Organo-chlorine residues in eggs of Buzzards Buteo buteo from the New Forest, Hampshire, during The weight of the egg content is given in grams. Analyses were carried out for the Nature Conservancy by the Laboratory of the Government Chemist using gas-liquid chromotography. Results are expressed in pas per million and refer to the entire egg content without the shell. f the amount of any paicular compound was 0. p.p.m. or more, this is given as a definite figure; if the amount was less than 0. p.p.m., this is recorded as 'trace'; a dash means that none was detected Weight Hepta- Eggs collected and Previous and subsequent egg pp'- pp'- pp'- chlor BHC Total Site Year breeding data site history content DDE TDE DDT Dieldrin epoxide isomers residues one from c/2; one Bred successfully 962, young reared 964,965, c/2 collected No information 962; pair present one from c/2; one _.,. r trace trace 0.3 young reared Pa,r present! ; f one from c/2; one \ one addled egg, one j young reared 966 y young reared J ' * trace trace one from addled Pair present ; old trace 0.8 c/2; second egg nest rebuilt 964 but no punctured eggs laid; pair apparently not breeding one from c/2; one Site not previously or trace trace 0.2 trace 0.4 young reared subsequently used one from c/2; one Bred successfully 962, young reared 963, 964; apparently not breeding one from c/3; two Bred successfully 962, trace 3.0 young reared 964, addled c/ Pair present 962; bred trace 5.4 successfully 963; pair present 964; apparently not breeding 966 EAN

11 BUZZARDS N THE NEW FOREST Analyses for organo-chlorine residues in eggs Table 4 shows the results of analyses for organo-chlorine residues in ten addled eggs collected by myself in the New Forest study area in 963,964 and 965. None was free from insecticide residues, although these were extremely small except in the case of an egg from site 20 in 965. All contained dieldrin and pp'-dde, and seven contained both pp'-tde and pp'-ddt; seven also contained heptachlor epoxide, but usually only as a trace. The mean figure for the total organo-chlorine residues in the ten eggs was.85 pas per million, DSCUSSON There are few earlier data on New Forest Buzzard populations from which to determine whether the degree of breeding success recorded during the study period was either smaller or greater than in the past. The verbal evidence of the New Forest Keepers suggests that the sizes of clutches and broods were smaller than previously, but it is difficult to obtain precise details and difficult, too, to establish whether these pre-date or post-date myxomatosis and the resulting decline of the Rabbit. A high incidence of infeility and non-breeding is reminiscent of the situation repoed from most pas of the country following the advent of myxomatosis and it is conceivable that during the study period a persistence of this situation was being witnessed. Six major factors seem likely to influence breeding success and population density in the Buzzard: the relative abundance of prey species (associated with competition with other predators); the availability of nest sites; drastic changes in the habitat; persecution; disturbance; and environmental contamination from the use of organo-chlorine pesticides (see oore 96$). The evidence suggests that only the first and last two factors could apply within the study area, but there appears to have been no firm association between them and the breeding success of the Buzzard population there over the five years concerned. On the face of it, the main prey species present in the study area are together sufficiently abundant to provide an adequate total preybiomass for the Buzzard population recorded. The main deficiences in prey sources appear to arise from the small size of the Rabbit population and the limited availability, because of its largely nocturnal habits, of the commonest small rodent, the Wood ouse. t may be that avian prey, because Buzzards possibly have greater difficulty in obtaining it, has failed to make good a deficit in mammalian prey. The argument appears thin, however, when it is remembered that the Buzzard was common in the New Forest before the Rabbit underwent the population explosion of the last three or four decades of the 9th century (see, for example, Barrett-Hamilton and Hinton 920: 2): in 39

12 BRTSH BRDS the New Forest the Rabbit does not seem to have staed to become common until the 850's and i86o's and it still could not have been described as abundant at the end of the 9th century. Disturbance may potentially affect breeding success, at least in individual instances. The New Forest is a popular recreational area and its use as such is increasing rapidly, but there was no direct evidence of any pairs of Buzzards being subjected to excessive disturbance. The disturbance inevitably associated with the study itself was also kept to an absolute minimum. Recent declines in the breeding success of some predatory birds for example, the Golden Eagle Aquila chrysaetos (Lockie and Ratcliffe 964) and in both the breeding success and populations of others for example, the Peregrine Falco peregrinus (Ratcliffe 963) show an association in time with an increasing use of organo-chlorine pesticides and it has been established that these species are subject to contamination through their prey. Ratcliffe (965) demonstrated that the Buzzard had similarly suffered a reduction in breeding success in the Lake District; eggs collected in 963 contained measurable quantities of pesticide residues, paicularly dieldrin, which he concluded had been obtained from carrion mutton and which would have derived originally from sheep dips. Prestt (965) also repoed recent declines in the Buzzard population in pas of nohern England, the idlands, Hampshire, Wiltshire and Dorset. Analyses of eggs collected from nests in the New Forest during the study period (see table 4) revealed only very small quantities of organochlorine residues, however. The mean figure for total residues (.85 p.p.m.) was lower than that recorded by Ratcliffe in the Lake District (2.5 p.p.m.). The New Forest is not sheep country and this is perhaps reflected in the low quantities of dieldrin recorded, although the higher concentration in the egg from site 20 is somewhat anomolous. The Forest and much of the area on its periphery is practically free from the agricultural use of pesticides and the main immediate source of the residues can only be the avian prey taken. any pairs of New Forest Buzzards prey extensively on Jackdaws Corvus monedula and it is possible that these are a major source of contamination since Jackdaws nesting in the Forest woodlands continue to feed extensively on agricultural land some distance away during the breeding season. n addition, some adults and probably most young Buzzards move away from the breeding areas during the autumn and winter months and may then be exposed to various sources of contamination. ACKNOWLEDGEENTS Without the assistance of G. B. Westerhoff, L. A. ummery, D. J. 392

13 BUZZARDS N THE NEW FOREST Chilcott, D. F. and R. Billett and, for pa of the time, G. H. Rees, who worked as a team with me, the data on populations and breeding success could not have been collected. y warmest thanks are also due to W. A. Cadman, Deputy Surveyor of the New Forest, both for the facilities always so readily given us during the study and for the loan of various items of equipment; to his Forest Keepers, both for help in the field and for a good deal of background information; and to R. E. Emmett, who provided essential items of climbing equipment. am also indebted to R. A. Fenton (Nature Conservancy) for drawing the map reproduced as fig. i on page 382; and to Dr. N. W. oore, an Prestt and Dr. Adam Watson for commenting on the paper in various stages of draft. SUARY Data were collected during the five years on the population of Buzzards Buteo buteo within 2.5 square miles of the New Forest, Hampshire. At least 33 or 54 pairs were consistently present in the study area during the breeding season each year. Prey collected from nests suggested that medium-sized birds (such as Jackdaws Corpus minedula and Jays Garrulus glandarius), as well as Rabbits Oryctolagus cuniculus and Wood ice Apodemus sylvaticus, probably constituted the main food sources during the study period. The breeding data obtained showed that clutches were comparatively small (average.8 eggs in 33 clutches in ) and that the output of young was low with failure to hatch and egg-breaking common. Ten addled eggs analysed for organo-chlorine insecticide residues revealed only very small quantities (mean total residues.85 p.p.m.). The evidence does not- permit any correlation between breeding success and the known factors which might adversely affect it. REFERENCES BARRETT-HALTON, G. E. N., and HNTON,. A. C. (920-2): A History of 'British ammals. London. HEN, E. (963): The Birds of Hampshire and the sle of Wight. London. DARE, P. J. (957): 'The post-myxomatosis diet of the Buzzard'. Devon Birds, 0: 2-6. KELSALL, J. E., and UNN, P. W. (905): The Birds of Hampshire and the sle of Wight. London. LASCELLES, G. W. (95): Thiy-five Years in the New Forest. London. LOCKE, J. D., and RATCLFFE, D. A. (964): 'nsecticides and Scottish Golden Eagles'. Brit. Birds, 57: EADE-WALDO, E. G. B. (900): n Victoria History of Hampshire. London, vol.. OORE, N. W. (957): 'The past and present status of the Buzzard in the British sles'. Brit. Birds, 50: (965): 'Environmental contamination by pesticides'. B. E. S. Symposium Ecology and the ndustrial Society. PRESTT,. (965): 'An enquiry into the recent breeding status of some of the smaller birds of prey and crows in Britain'. Bird Study, 2: RATCLFFE, D. A. (963): 'The status of the Peregrine in Great Britain. Bird Study, 0: (965): 'Organo-chlorine residues in some raptor and corvid eggs from nohern Britain'. Brit. Birds, 58: WSE, J. R. (863): The New Forest, its History and Scenery. London. 393

14 Appendix. Known breeding history of Buzzards Buteo buteo in study area in New Forest, Hampshire, Successive figures between oblique strokes indicate the '2/empty', '2/broken' or '2/addled' mean that incubated following: clutch size/number of infeile eggs/number of clutches of the size indicated by the figure before the young dead on nest/number of young reared ('reared' is oblique stroke subsequently either disappeared, were defined as capable of sustained flight). Where it was broken, or were found to be addled. '?/empty' means that unceain whether it was an egg or a young bird which had the nest was not examined, but that it was brooded on been lost from the original clutch (i.e. those instances consistently during the incubation period and on examinawhere on a first visit the clutch was complete, but on a tion during the fledgling period was found to be empty, second a number of young smaller than the size of the '?/deseed' means that the nest was not examined, but clutch was found), losses are indicated by question marks. that it was brooded on consistently during the incubation For example,'3///'means that of a clutch of three eggs period and was subsequently deseed (this applies only one was infeile, two young hatched, one died and one to site 30 in 964 and 965). 'Present' means that a pair was was reared; '3/?/?jz' means that of a clutch of three eggs present, but that no breeding data are available. 'Not either an egg or a young bird was lost and the remaining breeding' means that a pair was present, but that the two reared; and '?/?//' means that neither clutch size nor behaviour of birds suggested that they were not breeding hatching success was known, but that one young was and no nest was found despite thorough searches. 'Nest found dead on the nest and one reared. A single figure on built' means that a new nest was constructed and lined or an its own means either (a) that when the nest was first old nest reconstructed and lined, but that no eggs were examined it contained that number of young and that these laid (for elaboration see page 385). 'Absent' indicates that were subsequently reared or (b) that young were found out Buzzards were absent from a site occupied in the previous of the nest, but close to it, at the end of the season. year. Site Present Not breeding 2 2 3/-//2 2/-/A 2//-/ Not breeding 3 Present Present 2/?/?/i /-/-/ 4 Not breeding Not breeding Absent 5 Present Present Present Present

15 '» f ft. ft. a. en 3 W - Ht - t* s K> * N> *>* H i - tj i ff a 5? Cfl TJ 8 hi f> it ft. z o "or N J 0 N s v -8 <8 '«.! & -J 8 9 re " r N Sv - tt 0! J * s K> to» z o - " n> ' n W - H o 3 - H s 8 N VO 00 5? a a s a? w -J z o «o a. 3 s? en i-t H 4 Wi s w - * v>» Z o S o* a - N» Z a a" 3 to K B S 0 rr 8 n GO Z a i H W 2: s ;» SO 0 5:!! r -j - u -it C\ " H. 5: J. H