Overwintering Surveys

Overwintering Survey Facts

  • During the spring, summer, and early fall monarchs are scattered across their range and would be difficult to count
  • In the winter, the monarchs gather at a few overwintering sites in Mexico, California, and some small sites in the deserts of the southwestern United States
  • For this reason, these overwintering sites are where volunteers and scientists go to estimate monarch populations
  • In Mexico, there are so many monarchs that scientists can't count them. Instead, they measure the area of trees covered by monarchs and use that to estimate numbers.
  • Along the coast of California, a team of survey coordinators (like us) work with volunteers (like you) to go out and count or estimate numbers at all the overwintering sites. These are called the Western Monarch Counts and are organized by the Xerces Society.