Showing papers by "Royal Society for the Protection of Birds published in 1990"
TL;DR: In this paper, the authors demonstrate that remotely sensed satellite imagery of this area can be used to make accurate predictions of the numbers of the dunlin Calidris alpina, and thereby assess the impact of forestry on this wading bird.
Abstract: THE Flow Country of northern Scotland is of international importance for wading birds, and has in the last decade been greatly affected by afforestation1, 2. Here we demonstrate that remotely sensed satellite imagery of this area can be used to make accurate predictions of the numbers of the dunlin Calidris alpina, and thereby assess the impact of forestry on this wading bird. The habitat favoured by dunlin is wet moorland interspersed with small pools ; they do not use large water bodies, built-up areas, woodland or agricultural land. We show first that the numbers of dunlin on 42 moorland sites, as surveyed in 1986 (ref. 3), are significantly negatively correlated to an index of soil wetness4, as provided by reflectance data from a satellite image of these sites taken in 1978 before afforestation. We then tested this relationship by using it to predict dunlin numbers on a random sample of unsurveyed sites. Subsequent surveying of these sites in 1988 revealed a good fit between predicted and observed numbers, and confirms previous independent estimates of dunlin loss4.
52 citations
TL;DR: In view of the 25% loss of native pine woodland in Scotland during the period 1950 to 1986, bird communities breeding in native Scots Pine (Pinus sylvestris) forest at Abernethy, Scotland, are described fromspecies densities estimated by point count methods and individual species densities were compared across gradients of habitat identified by ordination techniques.
Abstract: In view of the 25% loss of native pine woodland in Scotland during the period 1950 to 1986, bird communities breeding in native Scots Pine (Pinus sylvestris) forest at Abernethy, Scotland, are described from species densities estimated by point count methods and individual species densities were compared across gradients of habitat identified by ordination techniques. Thirty-five bird species were recorded with a total density of 29.9 individuals ha -1 of which 8 species, Goldcrest, Chaffinch, Spotted Flycatcher, Coal Tit, Crested Tit, Siskin, Treecreeper and Redstart, constituted 85% of numbers. Detrended correspondence analysis was used to ordinate vegetation at point count locations from which 14 groups of bird counts were analysed across the habitat gradients. Two axes, representing increasing openness of canopy (axis I) and decreasing shrubbiness (axis II), were identified. Total bird density declined significantly with openness of canopy and increased significantly with increasing (a) pine density, ...
43 citations
TL;DR: By spending more time feeding, dippers on acidic streams will have less time for other activities such as self-maintenance and predator surveillance; they may also be less able to meet the additional demands accompanying the initiation of breeding.
Abstract: The time-activity budget and energy expenditure of a riverine bird, the dipper Cinclus cinclus, was studied from March 1988 to July 1989, across a range of streams of contrasting acidity in upland Wales. Differences in time-activity budgets of birds on acidic and circumneutral streams were consistent with documented differences in prey availability and diet. Birds spent a significantly greater proportion of their active day foraging, swimming and flying, and less time resting, on acidic streams. Activity measurements varied significantly through the year, through the day, and with river flow. Despite differences in time budgets, mean Daily Energy Expenditure (DEE) on acidic streams was only 4.5–7.0% greater than on circumneutral streams. However, rates of energy gain were greater for dippers on circumneutral streams for every month of the year, a pattern confirmed by differences in body condition. By spending more time feeding, dippers on acidic streams will have less time for other activities such as self-maintenance and predator surveillance; they may also be less able to meet the additional demands accompanying the initiation of breeding. These findings are discussed in relation to the feeding ecology and breeding performance of dippers on streams of contrasting water quality in upland Wales.
35 citations
TL;DR: Concentrations of DDE in Dipper eggs were generally lower than those in raptors, but HEOD and PCB levels were similar to or sli...
Abstract: Deserted or addled eggs (n = 63) were collected from 34 nests of the Dipper Cinclus cinclus in Wales during 1988, while 14 eggs were collected from 8 nests of the Grey Wagtail Motacilla cinerea. A minority of eggs contained HCH and HCB, and only one Dipper egg contained mercury, but all or most contained HEOD, DDE and PCBs. Geometric mean concentrations in Dipper eggs were 3.26 p.p.m. lipid for HEOD, 4.51 p.p.m . for DDE, and 17.78 p.p.m. for PCBs. Concentrations in Grey Wagtail eggs were only slightly higher. In 7 clutches of 3 or more Dipper eggs, within clutch variation was greater than between clutch variation. For clutches of 2 eggs or more, there was significant variation between clutches for HEOD and DDE, but not PCBs. Most variation in DDE levels was due to low values at high altitude sites in upland sheepwalk, whilst high PCB values were found in 2 afforested catchments. Concentrations of DDE in Dipper eggs were generally lower than those in raptors, but HEOD and PCB levels were similar to or sli...
32 citations
TL;DR: In this article, the authors found that adults showed strong fidelity to breeding sites, only 3.6% (of 138) moving more than 2.5 km between breeding attempts, whereas 30% of birds ringed as nestlings moved more than 5 km and up to 32 km from natal sites.
Abstract: Between 1978 and 1986, 2500 nestlings and 700 fledged Dippers were ringed on rivers in mid and south Wales. Adults showed strong fidelity to breeding sites, only 3.6% (of 138) moving more than 2.5 km between breeding attempts. By contrast, 30% (of 166) of birds ringed as nestlings moved more than 5 km and up to 32 km from natal sites; post-natal dispersal involved significantly greater distances in females than males, with females significantly more likely to cross watersheds. Dispersal distance showed no correlation with time of fledging in either sex. Actual distances of post-natal dispersal in both sexes were greater than those expected from juveniles replacing likely adult mortality. We discuss our findings in relation to general hypotheses on breeding systems and dispersal patterns.
29 citations
TL;DR: A re-survey of wetland vegetation on the Ouse Washes in 1988 showed that it has changed dramatically in 16 years as discussed by the authors, with increased flooding probably the single most important factor.
21 citations
TL;DR: Investigating the effect on the three major invertebrate groups—Diptera, Hemiptera and Arachnida—together with total invertebrates and total biomass of coppice species living under oak Quercus standards at the Blean Woods complex in Kent finds densities and biomass values were highest in hornbeam and lowest in sweet chestnut.
19 citations
TL;DR: The breeding nightjar population at Minsmere RSPB reserve, Suffolk (TM 465675) has increased significantly from 8 to 23 churring males since management was initiated in 1978.
10 citations
TL;DR: The relative frequency of group roosting was assessed from 307 visits spread across the year to 98 bridge roosts, finding that for much of the year, most birds roosted in 'pairs' consisting more often than expected of a male and a female.
Abstract: Previous studies of Dippers Cinclus cinclus revealed that, although they are territorial and feed in a solitary way, groups of several individuals sometimes gather at roosts. We assessed the relative frequency of group roosting from 307 visits spread across the year to 98 bridge roosts. Although 9 birds were present at some sites, the majority of sites held only 1 bird. For much of the year, most birds roosted in 'pairs' consisting more often than expected of a male and a female. Sex ratios were around 1:1 in roosts of all sizes, though first years made a proportionately greater contribution to larger roosts. Roost size increased during the winter probably because birds from natural sites moved to bridge sites. The latter probably offered warm conditions during a cold period. While these features suggest some meteorological influence on roosting behaviour, the numbers of birds roosting at each site could be explained in part by the number of niches available, the local density of Dippers able to fill them...
4 citations