MEXICO CITY (AP) — A Mexican government report says the number of monarch butterflies wintering in Mexican forests has declined for a second consecutive year.

Alejandro Del Mazo is Mexico's commissioner for protected areas and he says the monarchs clumped in trees covering about 6.12 acres (2.48 hectares) this winter. That is down about 14.7 percent from the 7.19 acres (2.91 hectares) the previous winter.

The monarch butterflies' migration is measured by the area they cover in pine forests west of Mexico City.

Millions of the butterflies make the 3,400-mile (5,500-kilometer) migration from the United States and Canada each year.

The World Wildlife Fund in Mexico participated in the annual study. Its director, Jorge Rickards, said Monday that a particularly busy hurricane season across the insect's migration route could have been a factor.