Each year, North America bears witness to one of its most amazing wildlife migrations on very small wings. Butterflies fly hundreds, or even thousands, of miles in search of better weather, food, and breeding sites. Their migrations, while perhaps less conspicuous than the migrations of birds or whales, are every bit as spectacular.

The most famous migratory butterfly is the monarch. In the fall each year, many millions of monarchs leave Canada and the northern United States in search of warmer climates. Many monarchs travel to overwinter in the mountain forests in central Mexico, where they cluster on the trees. Monarch populations located west of the Rocky Mountains, meanwhile, often migrate to coastal California. A monarch's migration is especially fascinating because no single butterfly completes it in its lifetime. The butterflies that migrate south in autumn live much longer than a generation of summer butterflies. They survive the winter and start their flight back north in spring, laying eggs along the way. Their offspring continue their northward journey.

Other butterflies also migrate to varying degrees. The painted lady is particularly noted for dramatic migrations. Sometimes huge swarms of them fly across western North America and, to the shock of unsuspecting observers, appear in streams of orange and black butterfly. Their movements have been linked to rainfall and the growth of annual wildflowers in the desert. Several smaller and shorter migrations also occur every year. Red admirals, cloudless sulphurs, and question mark butterflies often fly southward as the weather gets cooler in the autumn, and return to their original breeding sites during spring. These shorter movements can be less predictable than those of monarchs, but they are nonetheless notable.

Scientists are learning a lot more every year about how butterflies navigate. Butterflies, including monarchs, are known to utilize the sun, their own biological clocks, and potentially even Earth's magnetic fields. Despite their fragile stature, they can navigate their way to locations they've never encountered.

Butterflies migrations also reveal some of the threats they face. Habitat degradation, pesticides, drought, and climate change all pose a danger to the availability of flowers that serve as food sources, or the host plants that larvae need for developing. Declining milkweed, for example, will directly lead to fewer numbers of the monarch species, since caterpillars need to feed on the plant. Gardeners and landowners can help to support the butterfly population by planting native flowers, adding milkweed to the garden if suitable, and limiting pesticide use. Even a few plants can provide a needed respite and a meal for a passing butterfly.

Monarch and other butterflies demonstrate how not all strong things come in large packages. Sometimes, they come with small, delicate wings and travel lightly and quietly with the shifting of seasons.