Coastal areas are crucial to numerous breeding bird species, but have undergone major changes because of anthropogenic development pressures such as altered land use and increased recreational activities. An understanding of what shapes species distribution patterns, and how human activities affect these patterns, is therefore necessary for marine management. The aim of this thesis is to investigate possible causes of spatial patterns of coastal breeding birds, and how human activities and environmental legislation affect these species. Forty eight coastal breeding bird species were surveyed in 4,646 squares of 1 × 1 km size, covering an archipelago in the Baltic Sea, on the east coast of Sweden. We classified all bird species as either specialist species, i.e. specialized coastal breeders, or as generalist species, i.e. species breeding also inland. Specialist species were found further out to sea, while generalist species were found closer to the mainland. The number of specialist and generalist species per square increased as total shoreline length increased, likely because of availability of suitable breeding habitat and feeding areas. Animal sanctuaries were significantly more effective in capturing specialist species and red-listed species than were unprotected areas, while nature reserves often were less effective compared to unprotected areas. Further, specialist species richness decreased as human shoreline exploitation such as buildings and jetties increased, while there was no significant effect on generalist species richness. Likewise, there was a higher probability of applications for exemptions from the general shore protection regulation to occur in squares with fewer specialist species. It is possible that habitats for specialist species are not appropriate for exploitation or that human disturbance make specialist species avoid exploited areas. The proportion of granted exemptions was very high (96%), and the areas they concerned were often close to previously exploited areas. Exploitation of shores is a continuous but slow process known as the cumulative effects problem or the ‘tyranny of small decisions made singly’, and this is difficult to tackle by environmental legislation. To conserve the breeding habitat along the shorelines in the archipelago, it is necessary to protect the shoreline against further exploitation, and appropriate management of unprotected shorelines is essential
