Earlier this year I was asked by Metroparks Toledo to start a program to monitor the dragonflies and damselflies at one of our local parks. I wrote a little bit about it in this post at the beginning of the summer, but now I’m finishing up the first monitoring season and have some thoughts about the experience.
Just to quickly recap for those who don’t want to click back and read the earlier post, the park system has some concerns about what might be causing a perceived decline in odonata at Wiregrass Metropark. This property is basically a small lake with a half-mile walking trail circling the water, and it’s known as one of the best parks in Toledo for watching odes. (This is where I led the dragonfly walk for Toledo Naturalists Association in June.) But Metroparks wants to gather data to see if there really is a significant decline happening here, and if so, to take action to remediate any negative environmental factors that might be contributing to it.
So we divided the lake into quadrants and I was to visit once in every ten-day period through the summer to do a survey. I counted the numbers of each species that I found in each quadrant, and made note of weather conditions on each count day. I thought I was pretty familiar with this lake from my own visits there to photograph odes in the past couple years, but I have a different relationship with it after visiting so often and watching things change week by week.
As you know, I’m interested in all insects, not just odonata. And I pay attention to plants too, especially noting what’s native and what’s not. My plant knowledge is much more basic than my bug knowledge though. I’ve enjoyed watching not only the changes in insects through the season, but the changing landscape when different plants are in bloom.
Dragonflies don’t have any connections to specific plants in the way that butterflies and moths do. For example, moth and butterfly larvae (caterpillars) are restricted to feeding on specific plants or plant families, so their populations fluctuate with the presence or absence of their host plants. Odes don’t tend to perch on flower heads because they’re not pollinators, but I’m always hoping for those extra nice photo opportunities when they do.
Some things that could impact the populations of odes at this location could be water quality, or the quantity of emergent vegetation around the edges of the lake. Many species of dragonflies lay their eggs in plants that grow in the water, so that when the eggs hatch, the larvae will be able to drop down into the water. Dragonflies and damselflies live most of their lives as underwater insects before crawling out of the water and becoming adult winged insects.
The northern half of Wiregrass Lake’s shoreline is pretty heavily vegetated, with the only access being provided by several stone fishing platforms. The southern half is much more open, and Metroparks has placed signs prohibiting shore access on the southern end of the lake, in hopes of protecting the habitat there. This is where I see most of the odes on my surveys, but I can’t be sure if that’s due to the particulars of the habitat or just because it’s the most accessible portion. There could be just as many dragons flying on the north end, but I can’t see the lake up there, except for a few small openings.
Some species are most likely to be seen flying over the water, like the Common Green Darner, Black Saddlebags, and Prince Baskettail. Others are often found on the land, like many of the pennants and meadowhawks. It’s always easier to get photos of them when they’re perched, but sometimes I manage to get in-flight shots of the ones that rarely land. This Prince Baskettail is a species that I’ve never found perched, but since it flies a shoreline patrol pattern that’s fairly predictable, I manage to get decent photos of this one usually.
My survey for the Metroparks doesn’t require that I take photos, but I try to photo-document at least one of each species so I can submit them to the three-year-long Ohio Dragonfly Survey. That statewide effort ends in 2019, so next year I won’t have to spend as much time taking photos and my ode surveys can be done in less time.
That raises another point about what I’ve learned from doing these surveys so far. In the past couple of years, I’ve relied heavily on my photos to help me confirm identifications of many ode species. Sometimes that’s necessary for the species that require up-close viewing of reproductive appendages, so that’s okay. But I found that I’d relied so much on my camera that I wasn’t able to identify many of the small damselflies in the field. As soon as I started these surveys, I realized that was a problem. On my first survey day, I had to take dozens of photos of damselflies, and then come home and sort through them all to confirm my counts. I tagged them all with their quadrant number based on the time stamps on each photo, so I could put them in the correct column of the count sheet after I identified them.
It was tedious, and that was not going to work for an entire summer!
Here’s just a sample of three species of bluets so you can see how similar they are — keep in mind that they’re about the size of a sewing needle. (You should be able to see them larger if you click on the photos.)
So, I immediately went to my field guides and forced myself to learn them better so I could name them in the field and not have to take so many photos. Things went much faster after I did that. You would think that someone doing insect surveys must be a very observant person, but I definitely have my weaknesses in that area. In fact, I wrote about an embarrassing episode of mistaken identify here. I still have to use my camera sometimes to see the detailed marking on the damselflies, but I can usually name them right away now, and don’t have to spend much time at home studying photos.
One other thing I learned is that it’s very difficult to count insects, especially the tiny ones. Sometimes as I move along the trail, I’ll count a Calico Pennant, for example. Then it flies off and I keep walking, and then I see another Calico Pennant land in front of me. Determining if it’s the same one or not is tough sometimes, but I do my best to decide if it could be the one I just saw earlier, or if it’s likely to be a different one. Believe it or not, sometimes I can tell individuals apart by the wear and tear on their wings, so that helps me to avoid double counting. And I’m sure I miss many more than I count, particularly the tiny damselflies that float around in the grass. But I’m hopeful that this survey method will still give us useful data going forward.
I’m so pleased that I’m able to do something worthwhile for Metroparks Toledo, and am also glad that this experience has improved my identification skills. I’m already looking forward to next year, to see how the numbers may be different and whether any new species will show up.