More Monarch butterflies appear to have made the long flight from the United States and Canada to their winter nesting ground in western Mexico, raising hopes after their number dropped to a record low last year. But experts still worry about unusual cold temperatures.

While an official census won't be ready until mid-January, observers are seeing healthy populations of butterflies, said Gloria Talavera, director of the official butterfly reserve.

Monarch populations are being hurt by various factors: in Mexico, the encroachment of logging into their habitat; and in the United States, the decline of milkweed, the butterflies' main source of food that has been crowded out by pesticide-resistant crops. - AP