Michał Polakowski, Monika Broniszewska, Łukasz Krajewski
Ornis Polonica 2016, 57: 83–106
https://doi.org/10.12657/ornis.2016.2.0
Abstract: The regular monitoring of ducks was conducted during spring migration in the Biebrza Basin in 2013–2015. The results were supplemented with data from irregular counts made in 1994–2015. In total, 452,292 individuals from 18 species were recorded in 2013–2015, and ca 1.5 million birds representing 25 species in 1994–2015. At the peak of spring migration the Biebrza Basin held the maximum of 60,000–90,000 ducks, yet the figures may be underestimated. The dominant species was the Eurasian Wigeon Anas penelope (60.3% of the recorded birds, 37,000–50,000 individuals during the migration peak). Other numerous species were the Mallard A. platyrhynchos (15.0%, up to 12,000–23,000 ind.) and the Northern Pintail A. acuta (10.4%, up to 7,000–10,000 ind.). The most important stopover sites were situated in the lower Biebrza Basin (mainly near Chyliny, Brzostów and at the mouths of the Kosódka and the Wissa rivers), in the Wizna Basin (the area of Grądy Woniecko and Wizna), and, prior to the dredging of the local streams, near the mouth of Brzozówka in the Middle Basin. This study confirmed the significance of the Biebrza Basin as the major national area of a global importance for the Eurasian Wigeon and Northern Pintail. According to the findings of this study, the site is also important for the Northern Shoveler A. clypeata, Mallard, Common Teal A. crecca and Garganey A. querquedula at the national scale.
Keywords: Biebrza Basin, ducks, spring migration, stopover site
