Krupa, Małgorzata, Mateusz Ściborski, Robert Krupa, Rafał Popis, and Justyna Wołoszyn. 2009. “Differences in Foraging Ecology of Wood Sandpiper Tringa Glareola and Ruff Philomachus Pugnax During Spring Migration in Sajna River Valley (nor Thern Poland)”. Ornis Svecica 19 (2). Lund, Sweden:90-96. https://doi.org/10.34080/os.v19.22655.