Title: Mountain birds – a comparative study from valley to mountaintop in a northern and southern Swedish fjeld   Author: Kristian Zackrisson   Abstract Main aim in this study was to increase the knowledge about birds in the Swedish mountain area. Three questions were asked: 1) Which bird species can be found during the breeding season along a low mountain slope from a forested valley to a mountaintop with bare mountain environment? 2) Do the number of species and individuals differ in different elevation zones? 3) Is the composition of bird species along a low mountain slope the same in the Kebnekaise mountains inLaplandand the Grövelsjön mountains in Dalarna? Bird census in two study sites located in the Kebnekaise mountains and the Grövelsjön mountains and subsequent analysis of the results from the bird census was the main parts in this study. Totally 20 bird species were found along a low mountain slope in the Kebnekaise mountains. In a lower elevation zone below the forest boundary there was 16 bird species and 509 individuals observed. 6 bird species and 65 individuals were registered in an upper elevation zone above the forest boundary. The lower elevation zone indicated a higher biodiversity for birds compared to the upper elevation zone. Bird species composition varied between the two study sites. Five species that had been observed in the Kebnekaise mountains where not found in the Grövelsjön mountains which instead had six species that were not found in the Kebnekaise mountains. Compared to other studies the 20 observed bird species are some of several species in the specific area. The higher biodiversity in the lower elevation zone can be related to declining temperature by elevation gradients. Previous bird censuses indicate that the bird species observed in the Kebnekaise mountains also can be found in the Grövelsjön mountains.