As migratory birds, Siberian cranes would fly south in fall and head back to western Asia in spring for breeding. Each year, a large number of the critically endangered cranes are stopping over at Momoge wetland, a nature reserve in northeast China. And for the so-called bird guardians, this season is their busiest time of year.
Greening America's Cities, A White House Policy Briefing on ideas and initiatives to green
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