Browsing by Subject "bird community"

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  • Hakkila, Matti; Abrego, Nerea; Ovaskainen, Otso; Monkkonen, Mikko (2018)
    Protected areas are meant to preserve native local communities within their boundaries, but they are not independent from their surroundings. Impoverished habitat quality in the matrix might influence the species composition within the protected areas through biotic homogenization. The aim of this study was to determine the impacts of matrix quality on species richness and trait composition of bird communities from the Finnish reserve area network and whether the communities are being subject of biotic homogenization due to the lowered quality of the landscape matrix. We used joint species distribution modeling to study how characteristics of the Finnish forest reserves and the quality of their surrounding matrix alter species and trait compositions of forest birds. The proportion of old forest within the reserves was the main factor in explaining the bird community composition, and the bird communities within the reserves did not strongly depend on the quality of the matrix. Yet, in line with the homogenization theory, the beta-diversity within reserves embedded in low-quality matrix was lower than that in high-quality matrix, and the average abundance of regionally abundant species was higher. Influence of habitat quality on bird community composition was largely explained by the species' functional traits. Most importantly, the community specialization index was low, and average body size was high in areas with low proportion of old forest. We conclude that for conserving local bird communities in northern Finnish protected forests, it is currently more important to improve or maintain habitat quality within the reserves than in the surrounding matrix. Nevertheless, we found signals of bird community homogenization, and thus, activities that decrease the quality of the matrix are a threat for bird communities.
  • Tiusanen, Maria (Helsingin yliopisto, 2018)
    For a long time protected areas have been vital in conserving species and biodiversity. But due to climate change it is important to study whether the protected area networks are able to fulfill their goals also in a changing climate. Because of climate change the amount of southern species is increasing. At the same time the number of northern species is declining as are the suitable habitats for them. In order to adapt to changes in the climate, species are forced to shift their distributions poleward and upward. As a result, species communities are changing and some species may be threatened with extinction. It is therefore urgent to study whether the protected areas can alleviate the effects of climate change and whether they are capable to protect biodiversity in a changing climate. The aim of the study was to investigate whether the protected areas in Finland have been able to alleviate the effects of climate change in the bird species communities. The study was based on line transect bird censuses carried out in 182 protected areas during the years 1980–1999 and 2000–2015. Community temperature index (CTI) was used to study bird communities’ response to temperature change. Thus, CTI is used as a climate change indicator. CTI is based on the average temperature of the species range. A higher CTI value therefore indicates that a higher proportion of birds in the community are warm-dwelling species whereas the low CTI value indicates the opposite. The aim was to find out how the size of the protected area, connectivity between the protected areas and the type of habitat had affected the change of CTI between research periods. Protected areas were divided into three groups based on their location: northern, central and southern parts. 14 models were built in each part, ranked according to their AIC values. Linear regression analysis was used as the analytical method. During the research period, CTI had risen in 155 protected areas indicating a change in the direction of warmer bird communities. However, we found out that certain features of protected areas were able to alleviate the effects of climate change. Better connectivity decreased the changes in bird communities in the northern and central parts. But in the southern parts a similar effect was not found, possibly due to the smaller size of the protected areas and the lower degree of connectivity. The larger size of the protected area was supposed to reduce the changes in CTI but the results did not support this hypothesis. In all parts open habitats were more effective in alleviating the effects of climate change than the forest habitats. On the basis of the results, increasing the connectivity between protected areas could potentially be advantageous for the species suffering from climate change.