Abstract
The breeding origins and racial composition of Redshank Tringa totanus wintering in the Cardiff area of the Severn Estuary were investigated using information from ring‐recoveries and biometric data. In total, between 1991 and 2000, we received 56 reports from the breeding season of Redshank ringed at Cardiff. These involved 36 different individuals, 31 reported from Britain and five from Iceland. There was a slight bias in records within Britain towards the north and west of the country. The proportion of adult Redshank of the Icelandic race T t robusta present during the non‐breeding seasons varied according to the month of capture and, importantly, between two neighbouring sites within the study area: Cardiff Bay and Rhymney. The latter site held a higher proportion of Icelandic birds throughout the winter. Percentages of Icelandic birds were lowest in October and November (2% and 27% at Cardiff Bay and Rhymney respectively) and highest in February and March (27% and 61% at the two sites respectively). The proportions of British Redshank T t brittanica in the populations at Cardiff were higher than in studies in eastern Scotland, Teesmouth, The Wash, Merseyside and north Wales but less than in north Kent. The apparent partial segregation of Icelandic and British Redshank between Cardiff Bay and Rhymney may have been related to differences in the availability of prey species at the two sites and/or a result of differences in the competitive ability of the two races. The segregation of Redshank between the two sites could potentially have increased the impact of the impoundment of Cardiff Bay in 1999 upon British‐born birds, though lessened the impact for Icelandic‐born birds. The potential for similar segregation occurring elsewhere in other species of migratory birds needs to be considered in determining the impact of any similar environmental change.
Published Version
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