The spring migration of the White Stork (Ciconia ciconia (Linnaeus)) and the Black Stork (C. nigra (Linnaeus)) over the Bosphorus, one of the migration bottlenecks of the eastern European population, was studied in 2006, 2008, 2009 and 2010 at a ridge north of Sarver close to the Black Sea. The number of White Storks counted per season was up to 119,381 in 2008, but it was less than half of that in 2006 and 2009. These big fluctuations do not reflect population trends but are probably due to slight shifts in migration routes from year to year. The number of Black Storks varied between 1,118 in 2006 and 3,052 in 2008. The medians of spring migration were 6 April for White Storks and 17 April for Black Storks.