The once-mighty monarch butterfly migration—an extraordinary natural phenomenon that passes right through our neighborhoods and fields—has been reduced to a trickle. Where were you all summer, did you notice?
For how things used to be, here is Annie Dillard describing the event in Pilgrim at Tinker Creek, published in 1974:
The monarchs clattered in the air, burnished like throngs of pennies, here’s one, and here’s one, and more, and more. They flapped and floundered; they thrust, splitting the air like the keels of canoes, quickened and fleet. It looked as though the leaves of the autumn forest had taken flight, and were pouring down the valley like a waterfall, like a tidal wave, all the leaves of hardwoods from here to Hudson’s Bay.
Dillard seems to be describing a scene of almost unimaginable natural wealth. The world had such an excess of raw material that it could make monarch butterflies not by the ones and twos, but by the millions. Indeed, estimates of the number of monarchs that used to overwinter in Mexican fir and pine forests range up to a billion. In pictures, the trees seem to be literally dripping with butterflies.