Each fall, monarch butterflies flutter south some 3,000 miles to winter roosts in Mexico.
North American monarch butterflies fly south every winter to wait out the cold in warmer forests in Mexico, often roosting in the same trees year after year, despite the fact that no individual monarch survives to make the trip more than once. Monarchs migrate much farther than any other tropical butterflies, moving as many as 3,000 miles, and are the only North American butterfly that does a round-trip migration every year. But their lives are short -- it's not their children but their children's grandchildren that make the next trip south the following fall.
Monarchs destined to make the fall migration -- those born in late summer and early fall -- act and develop differently than their counterparts born in early summer, who will not live long enough to make the arduous journey. They mate less and eat more, and they live for eight months instead of six weeks. When the fall-born monarchs emerge from the chrysalid stage, they don't bother to mate or lay eggs -- that will have to wait till spring. Instead of devoting their lives to reproduction, like their shorter-lived relatives, they focus on travel preparedness, putting all their energy into storing fat for the flight.
Once they start the long trip in August, these otherwise solitary creatures gather together to forage in large groups on nectar sources along the way. They have to move south before the onset of serious cold, since, being cold-blooded, they can't fly at all once it gets too chilly. They do stop to sip nectar regularly as they migrate, actually putting on weight over the course of the trip.
Although much remains to be discovered about monarch behavior -- how do these tiny, frail creatures cover such great distances so fast, and how do they locate the same roosts every year? -- scientists currently believe one factor that allows these orange-and-black wraiths to perform their epic migratory feat is their ability to take advantage of air currents to glide southward with relatively little energy expended.
Where to See Them: Large groups of migrating monarchs can be seen alighting on shrubs and trees along the coastal dunes and beaches of the Harbor Bight region. Good sites for spotting them include New Jersey's Cape May and Jamaica Bay in New York City.
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Migrating Songbirds: The Harbor Bight is smack in the middle of one of North America's chief corridors for migratory songbirds -- the Atlantic Flyway. In the fall, southbound landbirds tend to stop short when confronted by a big stretch of water, which makes for good concentrations of these itinerants (warblers, vireos, flycatchers, tanagers and many others) along the entire south shore of Long Island.
But even better is New Jersey's Cape May. This peninsula stretching south into Delaware Bay is a world-famous "landbird trap" where astonishing numbers of songbirds can be seen, including many stray "accidentals," or birds that aren't supposed to be in the region.