One of the best experiences in my life was migration of Common cranes in Serbia. Each year they stop at Slano Kopovo reserve to rest and regain strength so they can continue towards Middle East and Africa. This time it was about 11k birds there. A smaller number - sometimes local birdwatchers estimate over 50k birds. We started to walk when it was still pitch black. We were about 2km away from the lake but we could already hear the noise. As we were approaching it got almost deafening - se could not talk - and we didn't want to raise attention either. We didn't want to get any closer not to disturb them. As soon as there was some ambient light they started to take off for feeding. group by group they disappeared in the sky. Later I realised there were also some duck and goose species there as well. We spend all morning there walking around and were surrounded by these birds. Also occasional harrier, buzzard and heron.