Long-term Monitoring of Breeding and Transient Bird Populations on the Courish Spit of the Baltic Sea

Since 1957, Biological Station Rybachy performs long-term monitoring of timing of spring and autumn migrations, timing of breeding and postfledging movements, dynamics of numbers of breeding and transient bird populations by standardized trapping in Rybachy-type funnel traps on the Courish Spit on Baltic coast. The results of monitoring strongly suggest that take place the long-term fluctuations of the timing migrations and numbers of local and transient populations. Current climate warming leads to earlier spring arrival not only in species that spend their winter within Europe, but also in long-distance African migrants. Colder weather, conversely, delays spring passage on 15–30 days. There are reasons to believe that climate change has influenced not only the timing of arrival to breeding grounds but also to the time of migratory departure from the winter quarters, both European and African ones. Climate change exerts a much smaller direct influence on the timing of autumn migration; the latter is more dependent on the timing of breeding. Earlier spring arrival usually leads to earlier breeding in the Baltic bird populations, which in its turn enhances breeding performance and leads to production of more young birds and thus to populations growth. Long-term monitoring of bird populations by Rybachy-type stationary traps is a powerful tool of studying the impact of climate on avian phenology and numbers.