Monarch

The monarch migration is one of nature’s most
spectacular events. Much as birds migrate to
take advantage of resources available across a
large landscape, North American monarchs
travel up to an astonishing 3,000 miles in an
annual migration from their summer breeding
habitat to overwintering grounds.
During the summer breeding season, eastern
monarchs spread across the eastern U.S.
and into southern Canada, laying eggs on
milkweed plants. Western monarchs make
use of milkweeds
across the western
states, primarily
west and south of
the Rockies, and
into southwestern
Canada.
In the fall, monarchs
feast on late-blooming
nectar plants along
the way to their
wintering sites. The
eastern monarch
population winters
in oyamel fir forests
in the mountains of central Mexico. While the
spring migration northward is completed over
the course of two or more generations, the final
generation of the year flies the entire way back
to these forests, new to them, but visited by
their ancestors a few generations ago. In the
same way, monarchs from across the western
U.S. return to eucalyptus, Monterey cypress,
Monterey pine, and other trees in groves along
the Pacific coastline, from Mendocino County
south to Baja, Mexico. Climatic conditions at
these sites allow monarchs to survive the winter
before beginning the return trek to their summer
breeding grounds.