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Dragonfly Science

key takeaways
Key Takeaways
Why study dragonflies?
Dragonflies and Damselflies
What's the difference?
survey
Survey Methods
How was data collected?
survey results
Survey Results
What have we learned?

Key Takeaways

Odonates – more commonly known as dragonflies and damselflies- give us important clues about a location’s water quality and ecosystem health. By monitoring dragonflies and damselflies every year, we can create a picture of the changes in composition and seasonality of local and migratory odonate populations. This can give us important information about changes in habitat quality as well as impacts of climate change. 

In 2016, JCWC volunteers began surveying dragonflies and damselflies in our watershed, and continued the surveys again in 2017. We have found a lot of valuable information from our surveys: 

  • The Johnson Creek Watershed is home to three of the five main species of migratory dragonflies in North America: the common green darner, variegated meadowhawk, and black saddlebags.
  • 2016: 
    • Two new species (Autumn Meadowhawk and Black Meadowhawk) were added to the list of observed species in Multnomah County!
  • 2017: 
    • Our 26 volunteers observed 23 odonate species in Johnson Creek!
    • Four species new to the project list were observed!
    • Out of our three survey locations (Westmoreland Park, Brookside Park, and Centennial Pond), Westmoreland Park had the greatest species diversity, with 21 odonate species observed!
    • The survey location with the lowest habitat quality (Centennial Pond) had the lowest diversity, with 15 species observed

If you’d like all the scientific details, check out the full reports!

2017 Report

2016 Report


How to get involved:

Help Johnson Creek Watershed Council document the distribution of dragonfly and damselfly species by participating in this year’s community science programs! Learn more here. 

Visit our iNaturalist page to check out the various species we have observed! 

Dragonflies & Damselflies

Dragonfly vs Damselfly

When talking about dragonflies and damselflies, we often just say “dragonflies” for shorthand. But this leaves out the poor damselflies, which are closely related. It’s actually pretty easy to tell the two apart! Just look at three key features- their eyes, body, and wings.

  • Eyes: Dragonflies have much larger eyes than damselflies– in fact, most of a dragonfly’s head is actually its eyes (they have excellent vision)! Damselflies have a bit of space between their eyes. 
  • Body: Dragonflies have bulkier bodies and are a bit shorter and thicker than damselflies, which tend to have narrow bodies.  
  • Wings: Dragonflies have their wings spread out horizontally while at rest, like an airplane, while damselflies fold their wings up and over or alongside their body when they rest.

Dragonflies and damselflies are a bit like cousins, and you can talk about both by using the special word odonate.

Odontos is a Greek word for tooth. Odonates are carnivorous as nymphs and adults, and the nymphs are characterized by toothed mandibles (jaws) at the end of a long, extendable mouth part. 

Odonates are compelling to learn about, and we still have much to learn. Here are some other cool facts about them! 

  • Dragonflies are predatory, capturing other insects in mid-flight
  • Dragonflies can spend several years underwater as larvae before emerging and transforming into winged adults
  • The longest-known insect migration in the world is undergone by a dragonfly called the wandering glider. In a migration that lasts for several generations, some populations of wandering glider travel 11,000 miles from India to southern Africa, twice the distance traveled by monarchs! 

Survey Methods

The goal of these dragonfly surveys is to document:

  • Diversity, or the number of species found in the watershed
  • Abundance, or how many of each species might live in the watershed. 
  • Timing of species’ occurrence: When do adult dragonflies and damselflies first appear in our watershed? How might this compare with other local areas, or with other years? 

From June to October 2016, nine dedicated volunteers surveyed two locations (Westmoreland Park and Brookside Park) for odonates. In 2017, the surveys were repeated with 26 volunteers and a third location (Centennial Pond) was added!

Survey methods were developed by Celeste A. Searles Mazzacano of CASM Environmental. Celeste was our entomologist extraordinaire and scientific advisor on this project.

How were the surveys conducted?

  • Volunteers conducted surveys about every two weeks.
  • Odonate activity fluctuates a lot with temperature, cloud cover, wind, and more, so the timing of surveys would vary based on when conditions were optimal. 
  • Surveyors were armed with useful equipment, including a net, hand lens, dichotomous key for identifying odonates to the family level, and a field guide to identify them to the species level. Volunteer teams walked transects along a water’s edge at the sites, taking photos and netting individuals when possible. 
  • They recorded species, abundance, genders, and reproductive stage. Early in the season, our teams were especially careful to avoid netting newly-emerged odonates by looking out for a soap-bubble appearance on their still-delicate wings. 
  • Data was reported on iNaturalist

The more these surveys are repeated, the better we will understand these species!

2017 survey transects for Westmoreland Park (left), Centennial Pond (middle), and Brookside Park (right).

Survey Results

The most common species you may find throughout Johnson Creek are the Tule bluet damselfly (Enallagma carunculatum), the Pacific forktail damselfly (Ischnura cervula), and the Blue dasher dragonfly (Pachydiplax longipennis). 

The odonates pictured above had the highest observed abundance throughout our survey locations in 2017! 

Number of Odonate Species Observed (2017)

Westmoreland Park had the greatest odonate diversity out of the three sites, with a total of 21 various dragonfly and damselfly species observed in 2017. 

Odonate Diversity Fluctuations

Our results from each site in 2017 shows how the timing of odonates changes throughout the summer months. The graphs below display the number of different species observed at each survey date. This data can help us better understand when certain species (including migratory and non-migratory species) are present in Johnson Creek! 

What can we learn from our results?

Over the past two years, our surveyors have added new species records for our site locations, as well as for Multnomah County. Monitoring odonate assemblages can help us determine whether restoration goals are being met. 

The first year of surveys at Centennial Pond were conducted in the spring and summer of 2017, where an in-line pond is going to be removed in the future; our survey data will help us make comparisons about pre- and post- restoration habitat changes. For more information about the restoration project, contact Restoration Project Manager Chuck Lobdell at [email protected] 

Our results can also help us observe and understand changes in the historic ranges of odonates. A few years ago, Portland was the northernmost record for the Flame Skimmer (Libellula saturata); the dragonfly species is now documented in Portland regularly, and documented in southern Washington in 2017, showing a possible northward range expansion for this species. Global climate change has been implicated in geographical range expansion of dragonflies in Germany and Japan. Collecting more data here will help the scientific community be able to monitor changes in odonate dispersal.