Showing papers by "Royal Society for the Protection of Birds published in 1995"

Mercury levels in seabirds from the Azores, Mid-North Atlantic Ocean

Abstract: Levels of total mercury were determined in body feathers of 257 seabirds belonging to seven species from the Azores Archipelago, Mid-North Atlantic Ocean. Mercury levels in adult birds showed highly significant inter-specific variations. Median levels were higher in small petrels (Madeiran storm petrel=12.5 μg/g; Bulwer's petrel=22.1 μg/g) than in shearwaters (Little shearwater=2.1 μg/g; Cory's shearwater=6.0 μg/g) and terns (Roseate tern=2.0 μg/g; Common tern=2.3 μg/g). Such inter-specific variability is discussed in relation to biological factors that may influence mercury dynamics in birds. Intra-specific variations in mercury levels were also found. Mercury levels were significantly lower in chicks than in adults of Cory's shearwater, Roseate tern and Common tern. The levels in chick feathers were 60–70% of those in adult feathers. In Cory's shearwater and the terns (Roseate and Common combined), mercury levels decreased significantly with increasing age of chicks. Mercury levels in adult Madeiran storm petrel showed pronounced seasonal variation, being about 50% lower in Spring breeders than in Autumn breeders. Mercury levels are compared with levels reported for seabird populations of the same or related species, from a variety of regions. The use of bird feathers to monitor mercury in the marine environment is briefly discussed.

The decline of the Corncrake Crex crex in Britain continues

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...

Nest-site selection by roseate terns and common terns in the azores

Abstract: Nest-site characteristics of Roseate Terns (Sterna dougallii) and Common Terns (S. hirundo) in mixed and unmixed colonies were examined at a number of sites in the Azores archipelago using discriminant analysis. Colonies were stratified and points located in a systematic way. Physical parameters, nearest-neighbor distance, vegetation cover, and density of nests were measured. Measured nest-site parameters were compared between species and with habitat points selected in the colony. Significant interspecific differences in nesting sites were found. Roseate Terns nested in areas with high relief and/or tall vegetation and with higher nesting densities. Common Terns selected more-open areas. There was considerable variability in nest-site selection of both tern species among colonies. Roseate Terns were more specialized as their nest sites differed more significantly than those of Common Terns from the available habitats. In contrast to findings of studies in North America, nest con- cealment by Roseate Terns did not influence hatching success. Competition may be important in nest resource partitioning in individual mixed colonies depending on colony size and habitat structure. The need to maintain/create optimal nesting areas for Roseate Terns is stressed. As habitat descriminators varied greatly between colonies, management should be planned on a colony-by-colony basis. Received 15 March 1994, accepted 15 May 1994.

A recovery plan for Roseate Terns in the East Atlantic: an international programme

Abstract: In 1987 an action plan for the recovery of the European populations of Roseate Tern Sterna dougallii was launched. Intervention on the breeding grounds has included the wardening of sites to prevent human disturbance, the provision of nest-boxes to discourage predation, patrolling and controlling to reduce predator presence, planting of Lavatera arborea to shelter nesting birds, and use of the media to establish local interest and commitment. Intervention in the wintering area has focused on Ghana and the reduction there of trapping pressure, through the “Save the Seashore Birds Project-Ghana”, which has involved site protection, legal reform, training, surveys and education programmes.

Changes in Stone Curlew Burhinus oedicnemus distribution and abundance and vegetation height on chalk grassland at Porton Down, Wiltshire

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.