Tomorrow's NOVA on PBS covers the great orange butterflies on their migration to Mexico:
Orange-and-black wings fill the sky as NOVA charts one of nature's most remarkable phenomena: the epic migration of monarch butterflies across North America. NOVA's filmmakers followed monarchs on the wing throughout their extraordinary odyssey. To capture a butterfly's point of view, camera operators used a helicopter, ultralight, and hot-air balloon for aerial views along the butterflies' transcontinental route.
I am confused on a few points about their migration, and number of generations each year. I thought it was 3 generations, one for Mexico, one on the migration north, and the third returns to Mexico. But according to this the migration to Canada takes two generations.
When migrating south they don't mention the California Coast or where the ones that fly through Florida end up. (Do they end up in Cuba?)
That said, the camera work was breath taking. (you can watch it online) I saw a lot of great native plants there that are excellent for getting Monarchs. My only complaint is how little they showed or mentioned Milkweed. They talk about how easily the Monarch could vanish or stop migrating, and go to some lengths to show Monarchs being killed, you'd think they would have promoted the host plant a little more.
I haven't watched television in many years, but it's things like this that make me want to return to that time suck--even if only for a brief bit of time. Monarchs. They are such a great passion of mine. I can't tell you how many pass through here on their way south each autumn, but I can tell you its breathtaking and mind boggling and awe inspiring.
Beautiful film, and fun to see two former professors of mine, Taylor (KU), Brower (UF).
My recollection is the show mentioned two generations moving northward, one that sort of stays in place while producing the fourth, this last being the one that flies to Mexico.
The migration to Mexico is the largest and thus the "sexiest" to conservationists, but you're right, there are other lesser migrations by this species in populations not only in North America, but in other parts of the world, e.g. Australia. A population in Hawaii is non-migratory, and also has a significant proportion with a white background, instead of the usual orange.