| Summary: | In this thesis I explore the importance of using different habitat types in winter for a migratory shorebird, the Icelandic Black-tailed godwit Limosa limosa islandica. Godwits use a mixture of estuarine and freshwater wetland habitats across all major wintering regions. The Irish wintering population of black-tailed godwits makes up c, 20% of the flyway population, and these birds use coastal mudflats and adjacent grassland habitats throughout the winter. In addition, very large numbers congregate on inland wetland ‘callows’ in late winter and spring. The Icelandic godwit population is currently increasing, however, numbers of godwits wintering in Ireland have not increased as rapidly as elsewhere in the winter range over the last 40 years. Using detailed behavioural studies, I show that grasslands in Ireland provide essential resources for godwits, as prey consumption rates on the mudflats are insufficient to meet energetic requirements. Despite their importance, grasslands receive virtually no protection. Surveys of field selection by godwits throughout southern Ireland indicate that small, enclosed fields are avoided but that godwits use large, open fields in both urban and rural dominated areas. Levels of urbanisation also have little impact on the use of resources on mudflats or grasslands by godwits. Candidate fields for inclusion within protected areas would therefore ideally be large, open fields situated throughout urban and rural areas. Finally, I explore the evidence for increasing use of grassland habitats by godwits wintering in the east of England, where rates of population increase have been particularly high and annual survival has been estimated to be lower than other winter regions. Count information and records of individually marked godwits indicate a rapid shift in habitat use since the 1990s, with inland grasslands now being used by large numbers of godwits. These sites are also being used progressively earlier in the winter, which may indicate that estuarine prey resources are also limited in the east of England. Thus, while there is evidence that estuarine habitats are preferred by godwits in winter, grasslands are also essential for maintaining a large proportion of the Icelandic black-tailed godwit population, and improving protection of these habitats should thus be a priority.
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