Wednesday, September 22, 2010

Migrating Monarchs

Monarch butterflies (Danaus plexippus)Last year, we removed most of the bush honeysuckle from the edge of the path adjoining the woods at the northwest corner of the bottom field near the orchard. This year, this cleared area is awash with volunteer brown-eyed susans (Rudbeckia triloba) and wingstem (Actinomeris alternifolia, image below). While we routinely observe Monarchs (Danaus plexippus) through the summer, this area has been visited by hundreds of monarch butterflies in the past two weeks; at any visit to the site now there are usually 20 or more present, both on the flowers and in the trees. These images were taken in the early evening, essentially standing still and rotating in place.

Monarchs (the State Insect of Illinois) are present in the state all summer, having up to three broods. But those that have become adults by September are ready to migrate south, either to the gulf coast or all the way to "traditional" breeding grounds in the highlands of central Mexico. These fall migrant Monarchs were born in Illinois or points north into southern Canada, probably three or more generations removed from their ancestors that left the winter roosting grounds last winter/spring. They have never made this trip south before, yet somehow they know when and where to travel. As many as 300 million will congregate in Mexico's Transvolcanic Plateau. How and why they pull off this feat is a mystery. Monarchs are the only butterfly that has such a fixed migration pattern; the migration behaviors of other butterfly species are much more erratic.

It's nice to see all these flowers still blooming and providing these Monarchs with some nectar as a source of energy for the next leg of their long flight ahead!

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