Showing papers by "Royal Society for the Protection of Birds published in 1991"

Exploitation of prey by a river bird, the dipper Cinclus cinclus (L.), along acidic and circumneutral streams in upland Wales

Abstract: SUMMARY. 1, The diet of ihe Eurasian dipper Cirtdus cincltis. a riverine bird from a globally widespread genus, was assessed through all stages of its annual cycle using published data and held studies from streams of contrasting chemistry. Time-activiiy budgets were also compiled throughout the year and used to estimate annual energy requirements from the stream ecosystem. 2. TTie annual energy requirements for a territorial pair ranged from 148,(KX) to 158,(XKI kJ yr ' depending on whether one or two broods were reared. After allowing for assimilation efficiency, these requirements were estimated to represent 10,5-11.0 kg dry mass of fish and invertebrates. Using representative values for territory size (4680-1 i ,250 m'), annual exploitation of secondarj' production was estimated at 0,93-2.35 g dry mass m~~, 3. Several features combined to focus the predatory load on certain organisms over different stages of the annual cycle. These included the availability and selection ol" alternative prey, the need lo provision nestlings with targe items such as trichopteran lar\'ae, and the use by females of calcium-rich prey such as fish prior to egg formation. 4. Across their range of territory size, annual exploitation (dry mass) by dippers was estimated at 0.06-0,29 g m " for Plecoptera,

Counts of male Black Grouse Tetrao tetrix in North Wales

Abstract: Attendance by male Black Grouse was studied at 4 leks in north Wales in spring 1987 and 1988. The number of males at individual leks varied depending on time of day and season. The highest counts were obtained in April and early May, 1 hr either side of sunrise. Counts were also made on 45 of the 91 recorded display sites in north Wales, mainly between 04.00–05.00 hours in May 1988 and the results compared with data collected in 1986. Twenty-nine per cent of sites had more males in 1988, 47% had fewer males and 24% were unchanged. Overall, numbers had apparently increased by 4% but this did not necessarily reflect changes in the population. Leks in forests had declined more than those on moorland. Recommendations are made for standardizing survey methodology and for monitoring Black Grouse populations in Wales.

Winter bird communities in woodland in the Forest of Dean, England, and some implications of livestock grazing

Abstract: Winter bird communities, sampled by transect methods, were compared between 9 woodland sites (1 ungrazed oak, 4 grazed oak, 4 grazed conifer) in the Forest of Dean Gloucestershire, during 2 winters (1984/85 and 1987/88). Ungrazed oak woodland had the highest counts of individual birds in both years. More species occurred in oak woods than in conifers. Ordination of the combined data from the 2 winters illustrated a consistent gradient of bird species composition (after the exclusion of 2 flocking species, Woodpigeon and Chaffinch), from evergreen coniferous to deciduous broadleaf. Green and Great-spotted Woodpecker, Hawfinch, Field fare, Brambling, Great Tit, Magpie and Siskin occurred largely towards the deciduous broadleaf end of the gradient. Classification of the bird data split the sites firstly into deciduous broadleaf and evergreen coniferous. In further sub-divisions, one group had tree species composition consisting largely of ungrazed oak for which the indicator bird species was Hawfinch. The in...

A review of reports of Buzzard persecution 1975–1989

Abstract: An analysis of reports of Buzzard persecution in Britain using data collated by the RSPB for the period 1975 to 1989 revealed records of 238 Buzzards that had been killed illegally. A comparison with the results of the 1981 BTO Buzzard survey showed that Buzzards are significantly more likely to be reported dead through persecution on the edge of their range in Britain compared with the middle of the range. Of all reported deaths, 39% occurred in March and April, and were largely attributable to the misuse of poisons. Three main poisons regularly killed Buzzards; alpha-chloralose, mevinphos and strychnine. During the period of the analysis, the number of Buzzards illegally killed and reported annually did not show any decrease. Persecution is still considered a factor likely to be contributing to the restriction of the Buzzard's range in Britain.

Recent changes in footpath width in the cairngorms

Abstract: Five popular footpaths which grew wider from the 1960s to the early to mid‐1980s were re‐measured in July 1990. Two did not widen further during 1986–90, but two continued to widen. The fifth path had not changed significantly in overall width since 1982, but had slightly less bare ground than formerly. The two paths which stopped widening are at lower and more sheltered locations, whereas the other three are high and exposed to an extreme climate, where plant growth is very slow. Changes in the five paths are discussed in relation to human use of the area. A substantial and/or prolonged decline in visitor numbers may be required if all five paths are to stop widening.

Sex differences in the behaviour and measurements of Common Snipes Gallinago gallinago breeding in Cambridgeshire, England

Abstract: Observations of behaviour and measurements of the length of the bill and outermost rectrices were collected from Common Snipes Gallinago gallinago breeding at the Ouse Washes, Cambridgeshire in 1984. The birds were either trapped on the nest during incubation or caught in elastic powered nets when they alighted on prominent perches. They were marked individually with plumage dye or radio‐tags. Perch‐trapped birds were subsequently seen perching and giving drumming and arched‐wing displays and are assumed to have all been males. Only nest‐trapped birds, which are presumed to be females, were subsequently found incubating. None were seen perching or displaying. Birds caught by both methods were found tending chicks. Male Common Snipes had shorter bills and longer outermost rectrices than females. By using a discriminant function incorporating these measurements 82–85% would be sexed correctly.

Factors influencing the biometrics of Grey Wagtails Motacilla cinerea and Kingfishers Alcedo atthis in Wales

Abstract: We assessed the influence of age, sex, time of day and time of year on the biometrics of Grey Wagtails and Kingfishers in Wales between 1982 and 1990, mostly along upland rivers. We also collected data on apparent sex ratios. During breeding, male Grey Wagtails could be differentiated on plumage and the sex ratio in the study population did not differ significantly from unity. On average, males had significantly longer wings than females by 1.1 mm (about 1%). Outside the breeding season, only adults could be sexed easily, and were markedly dominated by males. This feature may reflect differential migration between the sexes, as in other motacillids, though more data are required. Moreover, many birds (44%), mostly in their first year, could not be sexed and the true sex ratio in the total wintering population remained uncertain. Adult Grey Wagtails reached their greatest weight during winter and their lowest following breeding, differences between these periods being around 19% of the lowest weight Increa...