In this Nov. 25, 2007 file photo a couple of monarch butterflies perch on a tree at the Monarch Butterfly Biosphere Reserve in the central Mexican town of Cerro Prieto.

On Monday Feb. 14, 2011, the conservation group World Wildlife Federation Mexico released a report stating that there is a partial recovery in the annual winter migration of Monarch butterflies to Mexico following a devastating 75 percent drop last year. (AP Photo/Miguel Tovar, file)