Flocks of migratory birds, particularly geese, have come to Sorkhrud wetland in the northern province of Mazandaran to spend the winter. The latest surveys in the current year put the number of migratory birds at around 550, compared with some 10,000 in 2016.

The annual census for migratory birds in Iran begins in the middle of the Iranian calendar month of Dey (December 22-January 20) and ends in the middle of the month of Bahman (January 21-February 19), through which Iran hosts rare species of migratory birds heading from north to the southern countries due to reduced seasonal temperatures and food availability.