What's small, has orange wings with black veins and flies to Mexico for the winter? Is it a bird, is it a plane? Nope, it's a monarch butterfly.
This very common butterfly—you see them all over Wisconsin, heads south every fall. It is the only northern butterfly that annually migrates both north and south, just like some birds. The difference between monarch migration and bird migration is that monarchs are a generational migrant, while birds are individual migrants. This means that, while the same individual birds will return next year, the next generation of monarchs return, not the same individual butterflies.
In the fall, monarchs head south. With a northerly wind, the monarchs will migrate at high altitudes, taking advantage of the tailwind. This helps them conserve their energy. As they travel, hundreds or even thousands may gather together at their nightly roosting spots.
Midwestern monarchs continue south all the way to the Sierra Madres of middle Mexico, where they spend the winter among fir forests at high altitudes. Winter monarch butterflies are kind of sluggish. On warm days they head out to look for nectar, but they don't reproduce. In spring they head north, breed along the way, and then die. Their offspring will return to the northern starting point, where they lay their eggs on milkweed plants.
So, the next time you see one of these winged wonders, think about the incredible journey this little butterfly will make. And, come fall, keep your eyes open for monarchs grouping together for their long trip to Mexico.