Nature Watch: The Flight of Dragons
About the author: Steve Ellis is a naturalist and Land Trust member who enjoys sharing his love of the natural world. His blog series, “Nature Watch,” will appear each month in “Habitchat,” chronicling native plants and wildlife you can expect to see during that particular time of year. We thank Steve for sharing his passion, illustrating the importance of island conservation.
Overview
Dragonflies require warm, sunny days in order to fly. August is the perfect month to observe the flight of dragons.
These winged predators start life as eggs that hatch into naiads (nymphs) in lakes, ponds or slow-moving streams. They are fierce predators, capable of capturing all manner of aquatic invertebrates. After transitioning through multiple growth stages, wings develop and the adults are ready to crawl from the water.
Adult dragonflies are primarily engaged in two activities: eating to sustain energy, and reproduction. Both require exceptional flying skills.
Dragonflies are quite accomplished predators, chasing down smaller insects in the air. They have a 95% capture rate, the highest percentage of any above-water predator. Peregrine Falcons, with all their speed and agility, only manage a kill on 50% of their attacks.
Many dragonfly species mate in the air, with the pair forming a living “wheel” shape. Fertile females then stay aloft, hovering to dip their abdomen in the water and lay their eggs.
The secret to this flying ability is found in the wings. Each of the four wings can be operated independently. The pitch – the angle of the wing from horizontal – is also changeable, which allows for amazing agility.
Other anatomical features aid them in flight. Their bodies are tapered to channel air over and under the wings and abdomen, reducing drag. This contributes to high flight speeds, with some species reaching 34 mph, the fastest of any insects.
Dragonflies have the ability to hover, fly upside down, go straight up or down, and make hairpin turns at top speed. They also can change course slowly, without stalling.
Dragonflies are important components of ecosystems. The naiads are top predators of underwater invertebrates and in turn fall prey to fish, amphibians and diving ducks. Adults capture countless flying insects including mosquitoes. In turn, they are prey themselves for birds such as American Kestrels.
To observe the flight of dragonflies, go to the shore of a pond or lake on a sunny day. Males of some species patrol a “beat,” hoping for a chance encounter with a female. Dragonflies also perch in the open on shoreline and emerging vegetation such as buckbean, pond lilies, willows and hardhack.
Dragonflies also show themselves far from water, hunting insects in sunny, open areas. Any dragonfly that is making sharp turns in flight is actively hunting prey.
There are several field guides that will aid you in identifying dragonflies. I recommend James S. Walker’s book, Common Dragonflies and Damselflies of the Pacific Coast, which offers life-sized photos of local species. Dragonflies and Damselflies of the West, by Dennis Paulson, is helpful if you like to travel.
Two particular sites online can help with identification. BugGuide.Net allows you to post a photo of an insect, which will be reviewed by experts. Another excellent site is Odonata Central. (Odonata is the order of insects that includes dragonflies and damselflies.)
Local photographer and dragonfly expert Mary Jo Adams has cataloged 20 dragonfly species on our islands. That’s a high number, considering the limited amount of impounded water available to them.
Dashing, acrobatic, and charming, dragonflies are worthy of observation.
Fauna: Eight-spotted Skimmer (Libellula forensis)
The striking wing pattern makes the eight-spotted skimmer one of the easiest dragonflies to identify.
Eight-spotted dragonflies are 2 inches long and have a wingspan that can reach over 5 inches. Both genders have two dark spots on each of their four wings. Males also show white spots between the dark areas, while female wings are translucent. The abdomen, the largest body segment, is brown with yellow stripes on females and young males. As they age, males develop blue abdomens and lose the yellow stripes.
Hatched naiads lurk on the muddy bottoms of lakes and ponds. They ambush a wide variety of aquatic invertebrates.
Emerging adults crawl out of the water at night and are ready to fly as sunlight warms the air.
Adult eight-spotted skimmers prey on mosquitos, termites, mayflies, small moths and other flying insects. They often glide when airborne, rocking back and forth in the manner of Turkey Vultures and Northern Harriers as they search for prey.
Mating in this species is a quick process, accomplished in flight. A fertile female deposits her eggs by tapping the tip of her abdomen on the water. She may concentrate on one spot or spread her eggs over a large area. The male often accompanies her.
Shorelines of muddy lakes and ponds with open water are the preferred habitat of this species. They also may be seen perched high in trees, far from ponds and lakes.
Flora: Hardhack (Spirea douglasii)
The common name for this shrub comes from the degree of difficulty to remove it from fields and pastures. It’s also known as rose spiraea.
Hardhack ranges in height from 2 to 7 feet. The leaves are oblong, reaching a length of 1.5 to 4 inches. They are dark green above and grayish-green on the underside.
The multiple branches of hardhack support numerous upright clusters of tiny pink or deep rose-colored blossoms. Blooming begins in mid-June and can last into September.
Bees, beetles, hover flies and butterflies pollinate the flowers. Tiny seeds held in clusters follow the blossoms.
Goldfinches and other small birds eat hardhack seeds. Deer browse the foliage, and the dense thickets shelter small mammals and amphibians. Bird species such as Marsh Wren and Common Yellowthroat build nests in the branches. Hardhack is also used as a host plant by pale tiger swallowtail butterflies.
Tolerant of water, this hardy shrub has been used in wetland restoration projects. It also has the ability to thrive in drier conditions.
Hardhack is one of the most under-appreciated native shrubs. It spreads easily from rhizomes and can quickly colonize disturbed places.
Look for hardhack along the edges of wetlands such as ponds, lakes and damp meadows. Many Land Trust properties have stands of this shrub.