Showing papers in "Bird Study in 1995"
TL;DR: In this article, the authors presented data on the spring arrival dates of 23 species of migrants in Leicestershire over a 50-year period and discussed the results in the context of global warming.
Abstract: Data on the spring arrival dates of 23 species of migrants in Leicestershire over a 50-year period are presented. Chiffchaff, Sand Martin, Blackcap and Sedge Warbler showed a significant trend towards earlier arrival over the period, while Tree Pipit, Cuckoo, Whinchat, Whitethroat and Garden Warbler showed a significant trend towards later arrival. Fifteen species arrived noticeably earlier in the 1940s, a period of warm springs, while several species showed earlier arrivals in the 1980s. A number of species showed later arrival dates in the 1960s and 1970s, when April temperatures were colder than average. Several species showed significant correlations between arrival date and temperature. Arrival dates of the earliest species were much more variable than those arriving later, while species arriving in the second half of April showed a generally synchronous arrival. The results are discussed in the context of global warming.
119 citations
TL;DR: It appears that lagomorphs were the primary prey which influenced the diet and breeding density of Buzzards in the study area and there was a significant negative correlation between nearest-neighbour distance and lagomorph abundance.
Abstract: The diet and breeding density of 19 pairs of Common Buzzard Buteo buteo¸ were studied in relation to indices of lagomorph and vole abundance during June July 1993 in a range of habitats in southern Scotland. Lagomorphs, voles and birds formed over 70% of the food items analysed from prey remains and pellets collected at nest sites. Indices of prey abundance differed significantly between habitat types. The percentage of lagomorph in Buzzard diet in different localities was significantly correlated with the index of lagomorph abundance; no such correlation was found between the percentage of vole in Buzzard diet and an index of vole abundance. The mean nearest-neighbour distance between Buzzard nests was 1.9 km. There was a significant negative correlation between nearest-neighbour distance and lagomorph abundance. It appears that lagomorphs were the primary prey which influenced the diet and breeding density of Buzzards in the study area.
71 citations
TL;DR: Responses from a questionnaire survey and from spring counts of males attending leks support the decline trends inferred from shooting records, with fewer estates in western Scotland having Black Grouse and those that had reporting declining populations more frequently and male densiti...
Abstract: Analysis of shooting bag records suggest a 90–¸93% decrease in numbers of Black Grouse shot in Scotland and northern England since 1900. The magnitude of the decline differed between regions; the most severe declines were found in western Scotland, where the highest numbers of birds were once shot, but where fewest are shot today. By contrast, numbers shot in eastern Scotland (Perthshire and Angus) have declined relatively little and this region is currently the stronghold for Black Grouse in Britain. Overall, numbers shot in Scotland and northern England have changed little over the last 40 years, but as only 25% of estates now shoot Black Grouse, shooting bags may no longer provide an accurate index of population trends. Responses from a questionnaire survey and from spring counts of males attending leks support the decline trends inferred from shooting records, with fewer estates in western Scotland having Black Grouse, and those that had reporting declining populations more frequently and male densiti...
51 citations
TL;DR: It is shown that by the late 1980s the Sand Martin population in central Scotland had recovered to the level typical of the early years of the decade, and keel-length, used as a measure of body-size, had assumed a similar value to that found before the population crash.
Abstract: Sand Martins experienced a dramatic population crash in Britain and elsewhere during 1983–84. Numbers breeding in central Scotland in 1984 were 27% of those in 1983, probably as a consequence of severe drought in the wintering quarters. Selection for small size during the population crash was demonstrated.1¸ This paper shows that by the late 1980s the Sand Martin population in central Scotland had recovered to the level typical of the early years of the decade. Moreover, keel-length, used as a measure of body-size, had assumed a similar value to that found before the population crash. The return of severe drought to the wintering grounds in 1990 was associated with a fall in both numbers and keel-length at the study site by 1991. We evaluate hypotheses which attempt to explain the positive correlation between body-size and colonysize, and conclude that the observed changes in mean keel-length are probably 'caused by selective mortality of different sizes of birds outside of the breeding season and probabl...
46 citations
TL;DR: A survey of Peregrines in the breeding season of 1991 gave an estimated total of 1283 pairs occupying known nesting territories in Britain and Northern Ireland 1214 territories were found occupied, 53 by apparently single birds, and 141 known territories (9%) were not visited Overall territory occupancy was 83% as mentioned in this paper.
Abstract: A survey of Peregrines in the breeding season of 1991 gave an estimated total of 1283 pairs occupying known nesting territories in Britain and Northern Ireland 1214 territories were found occupied, 53 by apparently single birds, and 141 known territories (9%) were not visited Overall territory occupancy was 83% The figure of 1283 pairs represents 147% of the overall population level believed to exist in 1930–¸39, and 167% of that counted during the previous national survey, in 1981 The net increase was geographically uneven, being greatest in a broad zone from the eastern Grampians to South Wales, whereas numbers were still well below pre-war level in coastal south-east England In coastal and western inland areas of the northern Highlands, numbers have declined since 1981 Throughout the UK, many coastal populations have substantial proportions of territories occupied by nonbreeding birds Population growth has involved both an increase in breeding density and expansion of breeding distribution, the
45 citations
TL;DR: A parallel study on Tawny Owls in Glen Urquhart showed a strong correlation between their annual breeding success and that of the local buzzards, which fluctuated on a 4 year cycle and was probably in response to vole abundance.
Abstract: The breeding success of 2 Common Buzzard Buteo buteo populations in the north of Scotland, were studied over the period 1977–¸89. Marked differences were found in breeding density, clutch size and nesting success. An examination of prey remains found at nests in the 2 areas provided a possible explanation. The more successful population in Moray were feeding on large prey items such as Rabbits and Wood Pigeons, whereas the other population in Glen Urquhart, fed more on voles and small passerine birds. A parallel study on Tawny Owls in Glen Urquhart showed a strong correlation between their annual breeding success and that of the local buzzards. This fluctuated on a 4- year cycle and was probably in response to vole abundance.
43 citations
TL;DR: Faecal analysis was used to investigate the relative contribution of arthropods and fruit to the premigratory diet of the Redstart and 4 European Sylvia warblers in Senegal in March and the warblers showed greaterPremigratory fattening and higher fruit consumption than the Red Start.
Abstract: Faecal analysis was used to investigate the relative contribution of arthropods and fruit to the premigratory diet of the Redstart and 4 European Sylvia warblers in Senegal in March. The warblers showed greater premigratory fattening and higher fruit consumption than the Redstart. Berries of the shrub Salvadora persica¸ were exploited by all species with berries over 5 mm diameter being selected.
42 citations
TL;DR: Refuse tips and fidelity to the breeding colonies explained most of the variation found, but the effect of these factors was age-dependent, adults tending to stay closer to the main breeding colony on the Medes Islands and the proportion of juveniles in the population increasing with the distance from that colony.
Abstract: The influence of several variables on the abundance of wintering Yellow-legged Gulls was assessed in 20 randomly sampled districts in NE Spain. Refuse tips and fidelity to the breeding colonies explained most of the variation found. However, the effect of these factors was age-dependent, adults tending to stay closer to the main breeding colony on the Medes Islands and the proportion of juveniles in the population increasing with the distance from that colony. Gulls were distributed among refuse tips in proportion to refuse availability, which could be interpreted as refuse tips being the preferred foraging area for the population.
42 citations
TL;DR: A census of singing Corncrakes throughout Britain was carried out in 1993 as discussed by the authors, where a total of 480 singing males were counted in 83 10-km squares in 83 islands of the UK.
Abstract: A census of singing Corncrakes throughout Britain was carried out in 1993. Ten-kilometre National Grid squares in Scotland which held the species in 1978179 and/or 1988 were searched systematically by night. Elsewhere records of singing birds were obtained by means of publicity and checked for accuracy. A total of 480 singing males was counted in 83 10-km squares. Ninety-two per cent of the population was found in the Hebridean Islands. The total count was 17% smaller than in 1988 and at least 34% less than in 1978. The average rate of population decline between 1988 and 1993 was 3.5% per year, which was more rapid than during the previous 10 years. There were considerable differences among islands and areas in the rate of change of the Corncrake population. In some areas the population had increased, but in Orkney there had been an 82% decline in 5 years. Areas with high rates of decline between 1978 and 1988 also tended to show rapid declines between 1988 and 1993. The census results and conservation me...
42 citations
TL;DR: This paper uses Common Birds Census data to examine habitat selection by Corn Buntings and the relationship between population change and land-use change at the scale of the individual farm.
Abstract: This paper uses Common Birds Census (CBC) data to examine habitat selection by Corn Buntings and the relationship between population change and land-use change at the scale of the individual farm. On each of 29 farms, structural data and cropping patterns in the year of peak Corn Bunting population size were compared with those in the year of lowest population size (or first year of extinction). Crop diversity, hedgerow length, field size and the areas of all crops except wheat and barley did not differ significantly between years of highest and lowest Corn Bunting population. Barley was more extensive in years of highest Corn Bunting population and wheat more extensive in years of lowest population. Variation in Corn Bunting population density in a sample of 18 farms censused in 1974 could not be explained by variations in habitat diversity, hedgerow length, field size, altitude or the area of different erop types. This variation was also unrelated to either of the first 2 components of an ordination of ...
31 citations
TL;DR: In this paper, the relative importance of different parts of extensive geographical areas for birds is evaluated using data from the New Atlas of Breeding Birds: 1988-¸1991 at the 2-km and at the 10-km square scale in a case study of the uplands of northern England.
Abstract: This paper provides a method for the evaluation of the relative importance of different parts of extensive geographical areas for birds. It uses data from the 'New Atlas of Breeding Birds: 1988–¸1991' at the 2-km and at the 10-km square scale in a case study of the uplands of northern England. Six important bird areas are identified, each consisting of a series of 2-km squares holding at least 1.5 times the mean regional species-richness and importance index of upland birds. Their relationships to existing Sites of Special Scientific Interest, Important Bird Areas and proposed Special Protection Areas are discussed.
TL;DR: Observations on selection of morphological traits in Darwin's Finches on the Galapagos Islands and results of a 2-way selection experiment on migratory behaviour of Blackcaps Sylvia atricapilla¸ have indicated that substantial changes can occur within short periods.
Abstract: The view on how rapidly morphological, physiological, and behavioural traits may change as a result of microevolutionary processes (i.e. genetic variation and directional selection) has changed considerably in the recent past. Observations on selection of morphological traits in Darwin's Finches on the Galapagos Islands and results of a 2-way selection experiment on migratory behaviour of Blackcaps Sylvia atricapilla¸ have indicated that substantial changes can occur within short periods. A striking case is represented by Blackcaps breeding in continental Europe. Within the past 30 years, a subpopulation has developed a 'new' migratory direction to the WNW to novel wintering areas on the British Isles. Experimental analysis of migratory orientation behaviour has demonstrated that behavioural changes can result from microevolutionary processes. Similar microevolutionary processes are likely to occur commonly, as both recent field observations and experimental results suggest. One outcome of this, which is ...
TL;DR: The fish community of Loch Lomond has changed rapidly in recent years following introductions of 5 new species of fish, and it would appear that this diet shift was not the result of a lack of available Roach, but was a functional shift in prey choice by herons to a more abundant, more easi...
Abstract: The fish community of Loch Lomond has changed rapidly in recent years following introductions of 5 new species of fish. The response of the most abundant resident, piscivorous bird, the Grey Heron Ardea cinerea, to the sudden arrival and rapid population expansion of potential prey species is evaluated here. The relative rate of predation of fish by herons during the breeding season and the size of the breeding population before (1978) and after (1990) new species invasions is compared. In addition the relative abundance of fish prey species after the introduction of new species is examined. In 1978 the discarded remains of fish below the nests of breeding herons was dominated by native Roach Rutilus rutilus (63%). By 1990, at the same colony, at the same time of year, discards comprised mainly Ruffe Gymnocephalus cernuus¸ (61%). It would appear that this diet shift was not the result of a lack of available Roach, rather that it was a functional shift in prey choice by herons to a more abundant, more easi...
TL;DR: In this article, the authors studied the diurnal and seasonal variation in line transect counts of moorland passerines and found that diurnal variation was more prevalent for moorlands than other parts of the world.
Abstract: (1995). Diurnal and seasonal variation in line transect counts of moorland passerines. Bird Study: Vol. 42, No. 3, pp. 257-259.
TL;DR: A survey of breeding Corn Buntings in Britain in 1993 was carried out by as discussed by the authors, where volunteers from over 1300 tetrads selected across the range of the species in Britain.
Abstract: This paper presents the results of a survey of breeding Corn Buntings in Britain in 1993. Numbers of Corn Buntings and land–use types and field boundaries present were recorded by volunteers from over 1300 tetrads selected across the range of the species in Britain. The British breeding population was estimated at around 20 000 territories. Bootstrapped 95% confidence limits differed from the calculated estimates by approximately 20%. Population sizes in different regions of Britain were positively correlated with the proportion of total farmland under tillage and cereals and with the total areas of tillage and cereals, but not with the proportion of tillage made up by cereals nor with the overall area of farmland. Densities in occupied 10-km squares were lower in regions which experienced the greatest declines in distribution between 1968–72 and 1988–91. Areas abandoned by breeding birds between 1968–72 and 1988–91 were higher in altitude and held more grassland and less tilled land than areas where bird...
TL;DR: Irish Dippers start breeding earlier, lay fewer eggs, fledge fewer young and have fewer second broods than most other populations.
Abstract: The breeding biology of Irish Dippers was studied over 12 years. A total of 501 nests was located, mostly at artificial sites, notably bridges. Irish Dippers start breeding earlier, lay fewer eggs, fledge fewer young and have fewer second broods than most other populations. The mean clutch size was 4.16 (±se 0.03) and the mean brood size at fledging was 3.48 (±¸se 0.05) per successful pair. The breeding biology is compared with other populations and some differences are highlighted.
TL;DR: A second partial survey of breeding Peregrines in the Republic of Ireland was undertaken in 1991, duplicating the methodology and areas covered 10 years previously as discussed by the authors, where the survey located 123 occupied territories; when corrected for incomplete coverage a total of 141 was estimated, an increase of at least 23-26% since 1981.
Abstract: A second partial survey of breeding Peregrines in the Republic of Ireland was undertaken in 1991, duplicating the methodology and areas covered 10 years previously. The survey located 123 occupied territories; when corrected for incomplete coverage a total of 141 was estimated, an increase of at least 23–26% since 1981. Birds have also recently spread onto quarries, mainly outside survey areas; these have been surveyed independently. Overall, there were an estimated 350–355 occupied territories in the Republic, 17–18% of which were in quarries. Breeding range is shown to be limited by weather, operating through the interaction of spring rainfall levels, cliff size and cliff orientation. On cliffs >¸36 m high untenanted territories are only found in high-rainfall areas and oriented NW to NE. With decreasing cliff size, the vacancies affect a broader spectrum of cliff orientations, and at lower rainfall levels. Most currently unoccupied natural cliff sites appear to be vacant because of weather limitations,...
TL;DR: The social organization and territoriality of a colour-ringed population of Black Redstarts Phoenicurus ochrurus was studied in a mountain area of southern Spain during 4 winters, showing a complex territorial system and no short-term benefits of being territorial.
Abstract: The social organization and territoriality of a colour-ringed population of Black Redstarts Phoenicurus ochrurus was studied in a mountain area of southern Spain during 4 winters. A total of 28 adult males and 112 grey birds (females and juvenile males) was colour-ringed. These showed a complex territorial system: 5 adult males defended stable territories, 6 adult males and 1 grey bird temporarily defended different territories throughout the winter while most of the birds were non-territorial. Grey birds were observed less frequently than adult males in the area. Territorial and non-territorial birds seemed to be resident in the area; many being recorded after 40 days during the same winter. Territoriality was correlated with plumage and body size. However, size was age-dependent but within the group of adult males, there was no difference in either size, body mass or fat score suggesting no short-term benefits of being territorial. However, the survival rate seems to be higher for adult males than for g...
TL;DR: In this article, the results of a study of Water Rails within a small (0.5 ha) inland reedbed at Newbridge-on-Wye, mid-Wales, during autumn and winter 1993-94 were reported.
Abstract: The elusive behaviour and preference for dense aquatic vegetation has resulted in a lack of information regarding most aspects of Water Rail Rallus aquaticus ecology. This paper reports on the results of a study of Water Rails within a small (0.5 ha) inland reedbed at Newbridge-on-Wye, mid-Wales, during autumn and winter 1993–94. Birds used a substantial proportion of the reedbed (captures made 30–¸60 m apart), occupying home ranges which appeared to overlap, although different individuals nevertheless favoured different areas of the reedbed. Evidence is presented that the site was deserted during a period of freezing weather, but that birds re-occupied their original home ranges upon their return. Frequent trapping of birds also permitted an estimation of absolute population density (14 birds per ha), a figure much higher than previously recorded at other sites where birds were counted only indirectly. These data indicate that trapping can yield valuable information on aspects of the ecology of this litt...
TL;DR: This work assessed whether a large gull roost, at a reservoir near Oxford, UK, could be moved by using taped distress calls and pyrotechnics without causing significant disturbance to wintering wildfowl.
Abstract: Daily gull movements between feeding and roosting sites may present a major hazard to aircraft. One option to avoid this problem is to deter gulls from using certain favoured roosting sites. This may be difficult as the gulls usually roost on water. We assessed whether a large gull roost, at a reservoir near Oxford, UK, could be moved by using taped distress calls and pyrotechnics without causing significant disturbance to wintering wildfowl. Gull movements were monitored during 3 deterrence trials by making weekly counts at several sites. These were compared with seasonal trends in gull numbers at a roost beyond the influence of these operations. Observations and counts were used to investigate the effects on wildfowl. These standard deterrence techniques prevented roost formation so long as an alternative roost site was available; they failed when alternative sites were frozen. Hence the pattern of gull movements in the area was considerably altered by their denial from this important roost. Gull roost ...
TL;DR: The distribution of 5 species of auks and 3 species of Procellariiformes in northwest European waters was analysed in relation to 5 depth zones and the presence of fishing vessels was considered to be of secondary importance for Fulmars.
Abstract: The distribution of 5 species of auks and 3 species of Procellariiformes in northwest European waters was analysed in relation to 5 depth zones. Auks and Manx Shearwaters were restricted mainly to the continental shelf. Fulmars and British Storm Petrels were found mostly in waters of greater than 100 m depth. Interspecific variation in distribution may be related to dietary differences. The presence of fishing vessels was considered to be of secondary importance for Fulmars.
TL;DR: The breeding biology and survival of the Alpine Chough Pyrrhocorax graculus in different European massifs (Alps and West- Balkan) is described and the effect of human food supplied by tourist activities, breeding success and flock structure were compared between 2 alpine populations.
Abstract: We describe for the first time the breeding biology and survival of the Alpine Chough Pyrrhocorax graculus in different European massifs (Alps and West- Balkan). When all data were pooled, mean clutch and brood sizes were 3.6 eggs (se = 0.1) and 2.6 chicks (se = 0.1), respectively. Fledging success per pair varied between 1 and 4 fledged young per pair (mean 1.9). Survival of the Alpine Chough was estimated with a capture-resighting model using a colourringed population (n = 315 adults) which used human food sources. Adult survival rate varied from 83 to 92%, depending on the flock. This difference could be a consequence of differences in flock composition. No significant difference was detected between male and female survival. Survival of first-year birds (77%) was lower than that of adults. In order to analyse the effect of human food supplied by tourist activities, breeding success and flock structure were compared between 2 alpine populations which either did or did not exploit human food supplied by...
TL;DR: It is concluded that natural feather patches resulting from kills are important for birds who need this nest material and suggested that Long-tailed Tits may be attempting to avoid competition for feathers by nesting early.
Abstract: The demand for feathers as a nest-building material was investigated by placing feather patches in woodland and garden sites between January and June 1993 and March and April 1994. The first of 18 species to breed in the area which use feathers in their nests was the Long-tailed Tit. The feather requirements of this species are known to far exceed that of the other species. Long-tailed Tits were shown to forage actively for feathers up to 115 m from the nest but possibly not as far as 200 m. Patches generally remained untouched during the 24-h exposure but when detected were typically heavily exploited. Complete disappearance of feather patches occurred sporadically right to the end of the study. The woodland contained only a low standing crop of moulted feathers and it is concluded that natural feather patches resulting from kills are important for birds who need this nest material. It is suggested that Long-tailed Tits may be attempting to avoid competition for feathers by nesting early.
TL;DR: In this article, the authors used the results of a systematic upland bird survey conducted in 1990 and the information held on BTO nest record cards to study the distribution, numbers and breeding ecology of Twite Acanthis flavirostris in the south Pennines of England.
Abstract: This study used the results of a systematic upland bird survey conducted in 1990 and the information held on BTO nest record cards to study the distribution, numbers and breeding ecology of Twite Acanthis flavirostris in the south Pennines of England. The survey estimated the size of the population as between 200 and 400 pairs. The distribution of records obtained during the survey is mapped. In the breeding season, Twite show an association with relatively low-altitude sites at the moorland edge, especially where the length of reservoir or river shore tends to be large and the sward height exceeds 5 cm. They apparently avoid areas dominated by Juncus¸ spp. flush vegetation. We compare information available on BTO nest record cards for south Pennines Twite with those from Scotland. Breeding performance for Twite nesting in heather-dominated habitats was better than for those nesting on either grassdominated or other moorland habitat. Twite brood-size in the south Pennines has declined in recent years and ...
TL;DR: The breeding distribution of Shorteared Owls in a large forest with a diverse age structure is described; peak densities occurred at 3–¸7 years, and the age of the trees was the best predictor of owl numbers.
Abstract: During the last 70 years Short-eared Owls have exploited the high vole numbers associated with the early stages of large afforestation programmes in northern Britain. As a result, both breeding distribution and population size have expanded. Now that many forests are maturing, this improved status may be under threat unless the owls can use new patches of young forest, created by a replanting programme. This paper describes the breeding distribution of Shorteared Owls in a large forest with a diverse age structure. Patches of new forest tended to be larger than replanted patches. In the first rotation, forests supported breeding owls for 12 years after planting; peak densities occurred at 3–¸7 years, and the age of the trees was the best predictor of owl numbers. Some patches of second-rotation forest also supported breeding owls, and the size of the patch was an important factor in determining whether it was used; the smallest occupied patch was 62 ha. Short-eared owls can continue to breed in replanted ...
TL;DR: In this paper, a comparison of measurements of sward height in 1989 and 1994 indicates that sward heights had increased at breeding sites on seminatural chalk grassland which were used when the number of pairs nesting on downland was increasing.
Abstract: Annual surveys of breeding Stone Curlews at the Chemical and Biological Defence Establishment at Porton Down between 1987 and 1994 indicate that it is an important site for the species, having held up to 12% of the national breeding population. However, the population and the proportion of pairs nesting on chalk grassland declined between 1992 and 1994 after an increase since 1988. A comparison of measurements of sward height in 1989 and 1994 indicates that sward height had increased at breeding sites on seminatural chalk grassland which were used when the number of pairs nesting on downland was increasing. The sites with the smallest increases in sward height were those at which Stone Curlews continued to nest. The changes in vegetation are believed to be attributable to increased rainfall and lower densities of Rabbits. The implications of the results for conservation and management are discussed.
TL;DR: This note documents an attempt made by a male Dotterel to raise a second brood after its first brood of young became independent.
Abstract: Although some waders (Charadrii) are known regularly to attempt to rear 2 broods in some summers (e.g. Ringed Plover Charadrius hiaticula, Little Ringed Plover Charadrius dubius l), this ability is not associated with Palearctic waders breeding at higher latitudes, except where one or more clutches are left in the sole care of previous mates. This note documents an attempt made by a male Dotterel to raise a second brood after its first brood of young became independent.