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Autumn Irruptions of Red-Footed Falcons Falco vespertinus in East-Central Poland

Golawski A., Kupryjanowicz J., Szczypinski P., Dombrowski A., Mroz E., Twardowski M., Kielan S., Antczak K., Pagorski P., Murawski M.

Polish Journal of Ecology

2017

Vol. 65, nr 3

423--433

The red-footed falcon Falco vespertinus inhabiting SE Europe is known for its irruptive migrations. Here we attempt to outline the causes (weather conditions, dietary composition etc.) of the irruptions in 2014-2016 in east-central Poland. From 2004 to 2016 a total of 2873 falcons were counted during 542 observation bouts. The speeds of E and SE winds in August and September differed significantly between irruption and non-irruption years and were 1.3 km/h faster in the irruption years. Other weather factors, such as the number of days with E and SE winds, air temperature and the global North Atlantic Oscillation (NAO) and Scandinavia (SCAND) indexes, did not differ statistically between irruption and non-irruption years. The remains of 813 prey items were found in pellets collected in August and September, with a 93% dominance of insects; 84% of these were Coleoptera and Orthoptera. The irruptions of red-footed falcons in 2014-2016 may be also associated with increase in the number of breeding pairs in SE Europe.