Autumn crane migration and climate change in the Carpathian Basin

Weekly counts of roosting cranes were conducted between 2006–2014 in all significant stopover sites of Common Cranes (Grus grus) in Hungary, as an extension of the survey programme performed in Hortobágy National Park since 1994. As a result, I detected consistently asymmetrical migration phenologies in Hortobágy, indicating a superposition of several migration waves. Cranes used nearly 60 roost sites in Hortobágy with the largest ones situated in extensive fishponds. In contrast, cranes migrating in Körös-Maros National Park started to overwinter regularly, increasingly roosting in dry wetlands. In Kiskunság cranes tended to stage for shorter periods than in Körös-Maros, with the largest flocks to be observed in Lake Fehér of Szeged fishponds and additionally in a number of alkali lakes. Cranes observed in the Borsodi Mezőség region are considered satellite flocks staging in Hortobágy, as shown by irregular fluctuations.

As a probable result of climatic variability, cranes migrating in Hortobágy have shown the advancement of first arrival dates and exhibited significant, positive relations with local mean monthly temperatures. Additionally, we detected a positive relationship between the Julian date of autumn migration peak and winter mean of the North-Atlantic Oscillation, indicating later autumn arrivals during warmer periods.