Monday, November 01, 2010

Kestrels & Dragonflies

This past weekend, two dragonflies flew into me in my front yard--a clear sign that these insects are migrating.

Migrating birds are easy to see at this time of year. They're recorded at "hotspots" like the Idaho Bird Observatory at Lucky Peak in the Boise Foothills. At the same time, dragonflies are also migrating through Idaho, particularly green darners.

These insects will migrate to the Southwest, where they will lay eggs and, most likely, die. The eggs will hatch and live underwater as nymphs. Eventually, these nymphs will pupate, and fly to Idaho as winged adults. How they know where to go remains a mystery.

Dragonflies migrate around the world; in fact, one of the longest migrations of any species is the 11,000-mile, round-trip migration of dragonflies from the Maldives to India.

Often dragonflies follow very similar routes to birds. It makes sense that they follow the same air currents and geographic features that make for easier flying. But is there more to these similar routes?

One researcher recently found that, around Lake Superior, there is a strong correlation between the American kestrel migration and the dragonfly migration. On days when few dragonflies migrate, few kestrels do.

It turns out that kestrels migrate high overhead in the morning, and then dip down to catch a few dragonflies as fuel during the afternoon.

What other birds follow the dragonflies? Do the kestrels that are common around southern Idaho at this time of year feed on them?

At times, it can seem that the world is fully explored, that there is little mystery remaining. But this is simply not true. As National Geographic begins its celebration of "Great Migrations" this month, it's obvious that there is still much about this phenomenon that we don't understand.

We're still finding new migration routes, even of large mammals like pronghorns. And the migrations of most dragonfly populations remain poorly understood.

Keep an eye out for dragonflies this month. And let us know if you see some kestrels following behind.

Photo: American kestrel at the Bureau of Land Management's Morley Nelson Snake River Birds of Prey National Conservation Area. Photo by BLM.

1 comment:

Ferd said...

My lucky daughter in Maumee, Ohio just got to witness this phenomenon at about 7PM today, 9/11/13. She saw thousands of dragonflies over a pond, and about 15 Kestrels darting through the swarm, feasting on them!