Showing papers by "Royal Society for the Protection of Birds published in 1992"

Individually distinctive bittern booms: potential as a census tool

Abstract: Assessment of the similarity of sound spectrograms of the loud advertising vocalizations of bitterns (booms) by observers using subjective, qualitative criteria shows that the booms of bitterns are individually distinctive. Multivariate quantitative measures also showed booms to be individually distinctive. Both qualitative and quantitative assessments showed that booms from the same individual are consistent within and between years. The usefulness of individual distinctiveness in vocalizations for collecting data on within and between year survival is discussed, as are the factors limiting the technique.

Changes in the status of waders breeding on wet lowland grasslands in England and Wales between 1982 and 1989

Abstract: A randomly selected sample of sites surveyed in 1982 for the Breeding Waders of Wet Meadows survey was re-visited in 2989 and information on numbers of breeding waders collected. This showed that over this period numbers of Lapwings Vanellus vanellus had declined significantly by 38%, whilst Oystercatchers Haematopus ostralegus had increased by 56%. There was no evidence of a change in numbers of Snipe Gallinago gallinago, Redshank Tringa totanusor Curlew Numenius arquata. In both 1982 and 1989 a high proportion of all Snipe and inland breeding Redshank occurred on nature reserves. Numbers of Snipe and Redshank (but not Lapwing) were less likely to have declined on reserves than on unprotected sites.

Habitat use and site fidelity of Green Sandpipers Tringa ochropus wintering in Southern England

Abstract: Between 1982 and 1991 Green Sandpipers were studied in mid-Hertfordshire through regular counts and observations of colour-ringed birds. Birds were present in the study area in every month of the year but only in low numbers during May. Overall, throughout the year, 35.1 % of the birds were found at gravel pit complexes and 37.8 % at disused watercress beds. There was a marked shift from gravel pits in summer and autumn to disused watercress beds and stream sides in winter. Colour-ringing showed that the population consisted mainly of birds which regularly spent the winter in the area; the overall return rate from one winter to the next was 83.5%. Individual birds changed sites between autumn and winter in a similar way to the population as a whole and, in mid-winter, were extremely faithful to particular sites to which they returned each year. The return rates from one winter to the next are negatively correlated with the number of nights with air frost in the first winter.

The numbers and distribution of Cirl Buntings Emberiza cirlus breeding in Britain in 1989

Abstract: In 1989 the Royal Society for the Protection of Birds in conjunction with the Devon Bird Watching and Preservation Society conducted a survey of Cirl Buntings breeding in Devon. These data were supplemented by records from other counties to assess the current status of the Cirl Bunting in Britain. Results indicate that the long-term decline in both numbers and range has continued and that the future status of the bird as a British breeding species is in jeopardy.

Breeding bird communities of broadleaved plantation and ancient pasture woodlands of the New Forest

Abstract: To compare the breeding bird communities, counts were made at a total of 408 points in 482 ha of oak plantations and 641 ha of ancient pasture woodlands of the New Forest. Thirty-three species were recorded in each woodland type and the overall breeding bird density was similar in each, with Blue Tit and Chaffinch the most abundant species. Measurements at each point showed significant habitat differences between the 2 woodland types although there was much overlap and, particularly in the plantations, considerable variation in structure. The habitat variables were used to distinguish those points where the structure was typical of the plantations from those where the structure was more characteristic of the pasture woodlands. Seven species were more numerous in areas where the structure was typical of the plantations (Blue Tit, Chaffinch, Robin, Treecreeper, Coal Tit, Blackbird and Mistle Thrush) and three species (Great Tit, Willow Warbler and Jackdaw) were more numerous in typical pasture woodlands. Es...

The role of the Orkney Islands as a spring staging post for turnstones Arenaria interpres

Abstract: Patterns of change in numbers and mass of Turnstones in two parts of Orkney during winter and spring were compared. On Mainland and South Ronaldsay, Turnstone numbers were generally stable during winter and then tended to decline in April, leaving few birds still present in May; prior to emigration an associated modest gain in mass occurred. In contrast, Turnstone numbers on Sanday and North Ronaldsay, in the north‐east of Orkney, increased considerably in late April and remained high well into May; large gains in mass were attained over this period and the proportion of adults caught was higher than that recorded on Orkney in winter. The possibility is discussed that Turnstones wintering on Mainland and South Ronaldsay migrate north in spring via staging posts in Iceland, whereas birds staging on Sanday and North Ronaldsay may fly directly to Greenlandic breeding grounds.

Behavioural responses of Black-headed Gulls and Avocets to two methods of control of gull productivity

Abstract: Because Gulls have been considered to reduce Avocet breeding success, the behaviour of Black-headed Gulls Larus ridibundus and Avocets Recurvirostra avosetta at Havergate Island, Suffolk, was analysed in order to compare the effects of two methods of Gull productivity control, (a) formalin injection of eggs and (b) nest raking. Of four lagoons, two were controlled by each method in a simple experimental design. Gulls breeding on different lagoons behaved similarly prior to control, although Avocets showed no such consistent pattern. During the period 0–60 min after control Gulls were significantly more active on the ‘raked’ lagoons than on those where clutches were injected, in which they returned to their nests. This difference between lagoons was long-lasting — Gulls from ‘raked’ lagoons showed significantly more disturbed behaviour and exhibited a greater frequency of aggression, both interspecific and intraspecific, during the 2-month period of the experiment. There were no determinable effects of tre...