The objectives of this thesis were to analyse the breeding population trends and distribution of the Common Cranes in Estonia and the availability of potential breeding habitat (I, IV), to describe nesting habitats in Estonia and to explore the relationships between habitat and nesting success and nesting phenology (II), to investigate the relation between the numbers and distribution of autumn staging cranes and agricultural land use (III), to examine the stability of the habitat network used by cranes (IV) and to study the long-distance migration pattern of cranes (V). The population of the Common Crane started to increase in Estonia since 1970s (I). In parallel, the mean density of pairs increased, and distribution widened all over the country (I). First time breeders started to occupy new suitable habitats for nesting (I). The extended distribution of the crane has been favoured by the good availability of potential nesting sites (IV). The Common Crane nesting sites are different wetlands in Estonia have similar water regimes, plant communities and microrelief. The preferred breeding habitats are mires (II). The breeding success is associated with quality of breeding habitat and distance between neighbouring nests. The beginning of egg laying has a significant trend of advancement over time. Human activity had a significantly negative effect on the breeding success of cranes (II). The Common Crane numbers in staging sites are positively correlated with cropping area of cereals and negatively with the extent of potato fields. Changes in the local numbers and distribution of cranes when staging during their migration depend on changes in agricultural land use in staging areas (III). Migration routes used by cranes form a widespread ecological network (IV). Despite the modest contribution of nature conservation to the population increase of cranes (IV), the conservation efforts to protect peatlands play key roles in conservation of the Common Crane in the longer term. The climate change scenario modelling suggests minimal impact on cranes in future (IV). Common Crane’s long-distance autumn migration strategies differed between northern and southern sub-populations by the density and location of stopovers, daily flight distances, and the total migration duration. Cranes used during migration both, time- and energy-minimization strategies (V).