Sixty three Black Necked Cranes arrived at Bumdeling in Trashi Yangtse by December 4. A few more are expected to arrive during the course of this month.
Bumdeling is one of their winter roosting grounds in Bhutan.
To keep track of the cranes, the park officials also count the cranes every alternative day.
As the sun rises, they fly in groups, and mostly in pairs, to their feeding ground in separate directions.
Last year, the park recorded arrival of about 110 Black Naked Cranes.
Pankey Dukpa, the Chief Forestry Officer at Bumdeling said, having no enough feeding ground at Bumdeling is the biggest challenge the Sanctuary has been facing over the past years.
According to the Park officials, the number of crane arrival in Trashi Yangtse has been decreasing after the flood at Bumdeling in 2004.
During the first week of November, the cranes come to Bumdeling for winter roosting, and at the beginning of March the cranes would fly back to the Tibetan plateau in Zhe Ga Tshey.