Impact of land use on breeding bird populations a case study of Vuosaari harbour construction

Urbanization in general and the spread of industrial construction into natural areas can seriously reduce animal populations. In this thesis, I used breeding birds to investigate the impacts of the construction of Vuosaari harbour, ship channel and road connections on bird populations of nearby area. We monitored bird populations in Natura 2000 area and seabird breeding islets during the construction of the new Vuosaari harbour (Helsinki, Finland) in 2001 2011. The harbour was built less than 300 m from Natura 2000 area. We compared the bird populations before, during and after construction to evaluate whether the changes observed were linked with the construction work in the nearby harbour area. Our results indicate that in the Österängen agricultural area the number of species and territories increased during and after construction, with more territories located closer to the road than before the road was constructed. Thus, road construction resulted in at least a momentary positive impact on bird populations. New grass and bush areas and even large rocky outcrops clearly benefited some species such as the threatened northern wheatear. The bird populations declined slightly several years later, probably the as a result of habitat succession. In the forest areas, the population trends of 23 boreal forest bird species were significantly positively correlated with population changes in wider areas in southern Finland. Although the population trends were slightly weaker in the Natura 2000 sites compared with the general situation of southern Finland, this difference was not statistically significant. In the Natura 2000 wetlands he numbers of species and territories varied between years and subareas, but we found no clear impacts of harbour construction on bird population trends. The bird population changes in nearest bay, Porvarinlahti, were not more negative in comparison with those of the two other bays. We found that the waterfowl reproduction success was very poor, and that the number of small predators may be reason for that. The more predators were hunted, the less waterfowl nestlings were observed at the same year. The archipelago seabird study revealed that the population trends of most species showed no substantial differences between the monitored islets near the construction area and the reference islets. In conclusion, the numbers of species and territories varied between years and subareas, but we found no clear impacts of harbour construction on bird population trends. Although the population trends were slightly lower in the Natura 2000 sites compared with the general situation of southern Finland, this difference was not statistically significant. Our results indicate that despite the construction work demolished bird populations at the construction site, the impact of the harbour construction work had only limited impact on population trends of birds in the Natura 2000 site. Perhaps other more general factors such as climate and changes in the non-breeding grounds were likely a more important driver of local bird dynamics. This monitoring project has shown how difficult it is to estimate possible negative impacts caused by a single construction project. Before the project started, biologists said that severe negative impacts are possible, and according to the so called precautionary principle construction of Vuosaari harbour should not be allowed. Monitoring lasted ten years, and we couldn t see any clear significant negative impacts caused by construction.