Description
The “Donji Srem” Sugar Plant lies south of the village of Sibac (between Sibac and Pecinci), about 50 km west of Belgrade. The sugar plant is operational and the ponds can be quite smelly. There are three large ponds and several smaller. The large western pond is too deep for shorebirds, so focus on the shallower eastern one. An asphalt road passes by the eastern pond, the site of the breeding colony of Καστανοκέφαλος Γλάρος, in some years with a pair or two of Μαυροκέφαλος Γλάρος among them. This spot is under-visited.
This site holds Μαυρότρυγγας and Καλαμοκανάς, together with (Ευρωπαϊκή) Καλημάνα, Μαχητής, Λασποσκαλίδρα, (Κοινό) Μπεκατσίνι, Δασότρυγγας, Πρασινοσκέλης, Λασπότρυγγας. Other birds to expect include Αετομάχος, Σκορταλλός, Βαλτοποταμίδα and Τσιχλοποταμίδα. Μαυρογλάρονο are present on migration, while Μουστακογλάρονο is present in the breeding season too.
Details
Access
On the map, I marked not just the site, but a bit confusing turn-off from the main road as the route. For driving directions, zoom in on the map and click on the "P" (parking) sign.

