Nest site selection of the Eurasian Crane Grus grus in Estonia: an analysis of nest record cards

We describe in detail the nesting habitats of the Eurasian Crane in Estonia and explore relationships between different habitat characteristics and nesting success. We analysed all 161 reported Eurasian Crane nest finds in Estonia. We found that the cranes favorite nesting habitats are different types of mire (71% of all nests), especially fens (44%). We conclude that, despite the fact that the Eurasian Crane breeds in different habitats, nesting sites include the same or similar structural elements (vegetation types, plant species and communities and elements of micro-relief). We found that the date of the beginning of egg laying is significantly related to the size of the nesting habitat and that the annual mean date of the beginning of egg laying in Estonia has advanced considerably during the period 1901 to 2001. We also discovered a significant relation between the distance of neighbouring nests (population density) and the brood size and a negative effect of human activity on nesting success

Changes in distribution and numbers of the breeding population of the Common Crane Grus grus in Estonia

The aim of this study is to analyse population trends and distribution of the breeding population of the Common Crane in Estonia. The population size and density of the Common Crane in Estonia has increased several times over the last 30 years (1910-2001). According to the most recent population estimatź, about 5800 pairs were breeding in Estonia in 1999. The mean population density of the Common Crane in Estonia was 17.4 pairs/100 km2. Most of the Common Cranźs are nesting in mires (5300 pairs, 9I%),pimarlly in fens (4200 pairs, 727o).The mean population density in fens, transition mirźs and raised bogs was 41.3, 38'3 and 15.9 pairs/100 km2,respectively. Several factors have probably contributed to thź recent increase in the Common Crane breeding population in Estonia, e.g. the emergence of new nesting sites connected to human activity, locally higher spring tempźratures and conservation activities

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation.publishedVersio