The Mini Migrants
by Josh Palumbo, Forest Management Coordinator
I welcome you to The Nature Foundation at Wintergreen’s attempt to bring some nature and knowledge into your home. The Nine Minute Naturalist borrows from NPR’s lovely 90-Second Naturalist podcast. Since we all have a bit more time on our hands, the goal is to take something that is happening out in our environment and stimulate your brain for roughly nine minutes. Don’t let something as “minor” as a quarantine to keep you from learning. I hope you enjoy!
This past week a group of enthusiastic raptor lovers gathered to see our favorite buteos, accipiters and falcons travel south. Instead of seeing a mass migration of beautiful raptors, we were witness to a much smaller migrant zipping past, the dragonfly. Hundreds of dragonflies whizzed past our overlook as we fruitlessly panned the skies for raptors. We were witness to the epic journey of dragonflies heading to wintering grounds. This edition of the Nine Minute Naturalist will focus on these wonderful mini migrants.
Dragonflies are of key ecological importance. The aquatic larvae and winged adults create a link between aquatic and terrestrial systems. Both larvae and adults are voracious predators. An adult can consume 15% of its body weight in prey each day including pests such as mosquitos and biting flies. They are also key food sources for fish and birds, including being an important food source for migrating raptors. Dragonflies are also incredible fliers. They are able to hover, dive, fly backwards or upside down and reach speeds of up to 30mph. Each of the four wings acts independently so if a wing is lost, dragonflies can carry on.
Each fall, these three-inch ariel speedsters head from points north into Canada down to the Gulf of Mexico regions. Wintergreen and the surrounding Blue Ridge is a funnel point for these mini migrants and late September is the best time to observe this phenomenon. The dragonfly we get to see whiz past us most is the common green darner. Not many specifics are known about what starts this mass migration but temperature and day length are likely candidates. As the approach of killing frost gets closer, the swarms grow in number. While mostly solitary travelers, dragonfly migrants have been known to swarm in large enough number to be picked up by radar as they were in the fall of 2019.
This epic mass movement from north to south and back again is not accomplished by one generation but instead three generations of dragonfly participate in this yearly cycle. In early spring, the first-generation transitions from larvae overwintering in sheltered southern ponds or wetlands into adult dragonfly and begin the journey north. Here the dragonflies lay eggs and die. The next generation hatches, goes through the larval stage into adult form and heads south where they once again lay eggs and die. This third generation will overwinter in the comfort of Florida, Mexico or the Caribbean until the cycle of eggs, death and birth starts again.
Scientists are still baffled how the same flight pattern is followed from generation to generation with no instruction or memory to guide them. Yet these amazing creatures find their way to appropriate locals so the cycle can be repeated year after year. Make your way to any overlook at Wintergreen to witness the 2021 dragonfly migration.