January 16 - Ohio Odonata Numbers
5 Year Ave on Observations and Species
Chart showing relative connection of the number of observations and distinct species. This chart is based on 5 year (2018-2022) averages for all of Ohio at 10 day increments through the Ohio Odonata flight season. You don't get species without observations, both have high numbers late-May to early-July.
Note the two scales, Species on left, Observation on right. Scaling is not perfect, but close. Species max peaks a little earlier than Observations. Species numbers stay a little higher relative to Observations as the season starts to wind down in late September.
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I’m certain that there are fewer species flying at the end of the season in comparison to the early mid-season. I suspect that observation activity is significantly impacted by the anticipated number of specimens and especially the number of species.
The greater their expectation of species diversity, the higher the level of human observation activity.
I agree, Jay, and I think your observation about expectations driving observations is especially insightful. I also think of the academic effect; historically in Ohio most species observations come from near colleges and outside of the school year. That was evident even with odes in the last survey (of course odes mostly fly in the summer anyway). One of the nice things about community science is that it breaks down that particular bias by putting a wide variety of people out there, most of them not tied to an academic schedule.
Jim, I really appreciate all of your data presentations. I keep wondering what the data can say (if anything, yet) about two big issues with insects: population declines (the "insect apocalypse"; certainly a concern in Ohio for native bees and butterflies) and impacts of climate change (changes to geographic or temporal range). Any thoughts?
Jim, I really appreciate all of your data presentations. I keep wondering what the data can say (if anything, yet) about two big issues with insects: population declines (the "insect apocalypse"; certainly a concern in Ohio for native bees and butterflies) and impacts of climate change (changes to geographic or temporal range). Any thoughts?
Yea, a few thoughts. Our current perspective on Ohio Dragonflies is better than ever. There are still a few weak areas in the data and some periods of the year that could be improved. People are responding to goals.
Our 5-yr average on species is right at 138/year. This means that recently, every year (2018-2022), we're seeing 80% of all the species that have even been recorded in Ohio. If we look at the number of species that have Ohio records in more than 10 years, the number is also 138. If we look at species that have over 25 -total- records, that number is 144. So, we are looking and seeing. Another metric I started last year was the number of species/county pairs for each year (I'll be sharing the updated chart on that.) All this goes to say "good job" on our survey efforts. I think we're on a good track for capturing data.
Our world is changing. Quickly. Things are different from 100 years ago, and also from 30 years ago.
Looking at the data - just straight up numbers, no statistics...
Some northern species appear to be gone (ex Canada Darner). Some species numbers are down because of photo ID issues (ex Ruby Meadowhawk). Some are probably down due to habitat loss/degradation (ex Rainbow Bluet, Lyre-tipped Spreadwing). Some things we don't fully understand (Baskettail complex, Macromia Hybrid.) Also, what's going on with the current void with some of the Mosaic Darners? or the Aurora Damsel? or the Eastern Red Damsel?
On the flip side, we are seeing record numbers on southern species. In recent years, things like Carolina Saddlebags, Slaty Skimmer, Great Blue Skimmer have been reported in unprecedented numbers.
Pond Skimmer numbers are good. Looking at any of the online maps shows many ponds that weren't here 100 years ago. Build it and they will come. These same species seem to do OK with human disturbance.
Aside from the data...
It seems to me like there's fewer bugs. And not just Odonata. Sure, there are still good days out, but less so than in the not too distant past. Especially noticeable at bigger streams, even with 50 years now of Clean Water Act. Interesting times.
I may be deluding myself, but I'd like to think that some of why I spend so much time on iNaturalist, and especially why I try to cover some of the same locations, year over year, is because a) its the last best chance to document what it is right now, and b) it could be useful to science, capturing the existence of a species, and its mating, flying, flowering timing, that is different in the future.
Wish I'd spent more time shooting dragonflies during vacations on our Coshocton property in the 00s, before we built a house and I had regular access to it. Slaty Skimmers are one of the dominant species in July. When did that start?
As recently as 2016 there were fewer than 10 Slaty Skimmer records in Jul for the whole state. In 2010 there was only 1.
would there be any value in implementing an event along the lines of the christmas bird count--select a day some time in mid-June and collect count estimates of all species observed within some defined area? I'm partly reflecting on my own reporting habits--I tend to report species sightings but not in a way that's quantitative. Just a thought; would that add data that improves understanding in any significant way?
All data contributes. Significance gets tricky. Goals help, would need to be flexible - more on the order of a week.
An Odonata count day sounds like a really cool idea! It would probably take years to gain a lot of info from such a venture, but there are probably enough interested parties out there to make something like that work. Documentation is also a potential issue, as it is not always possible to get a photo of a bug. In birding, that is not a huge issue historically, although the trend is that rare things ought to be documented because of the improvements in technology with digital recorders and cameras.
Some additional thoughts on the statistics of observations...
1) As stated above, it is not always possible to get a (good) photo of a bug that allows a valid ID...so true...this is especially true of dragonfly fliers (common green darner is a prime example...it should be near the top of the observation list in my opinion because it really is common, but it is so hard to get a good picture of it, it never will be...I sometimes need to take 20-30 pictures of the green darner to get one good one, if it hangs around long enough)
2) observation strategy issues...I may be the exception, but after I take 2-3 good pictures of the same species (common odes, making sure they are far enough apart to be separate individuals) at a specific observation site on a specific day, I stop taking pictures of them and concentrate on the not so common bugs...this results in underestimates of certain odes. Maybe this doesn't really matter since maybe we ought to focus on the least common odes.. (This issue leads me to believe that number of days species observed may be a better estimate of their population health (especially for fliers, but of course the length of a species flight time will need to be factored in...this begs the question...what is the best way to determine the most common dragonflies in Ohio?))
3) Year-to-year weather variability will probably impact the statistics. A particularly cold winter may decrease the following season ode population for example. Or maybe a late Spring freeze or early Fall freeze is the key factor.
4) As mentioned above, habitat is another critical factor in the yearly statistics, but the year-to-year impact should not be too high in my opinion as the number of increasing or decreasing types of habitats won't change very quickly. However, over time this will be (probably has been) important. The number of small drainage ponds in large suburban housing areas is greatly on the rise.
5) Ode predators probably need to be taken into account somehow...I'm no expert on this, but the populations of predators must vary from year-to-year and impact the number of odes observed.
6) Observation errors in general ...may be a training issue, but how do you make sure observers aren't taking pictures of the same ode over and over again at the same site on the same day or following days (within the life span of the species). Or there may be two observers at the same site on the same day or with a few days. Of course this may be a rare event type issue that can easily be ignored. However, I think it is probably happening at such sites as Cedar Bog.
7) Observation sites that are difficult to get to may be an issue. Some are physically hard to navigate (such as rivers) and others may have limited access or be far to remote from where most observers live. Based on my energy level and commitment, I prefer local ponds or wetlands...the low hanging fruit. Many others may be up to the challenge for difficult areas and Jim is good with putting the challenges out there. Another issue may be the lack of observation sites in some counties with few parks, lakes, rivers, or wetlands.
Many of these same issues arise with bird counts. Photos aren't required for the annual Christmas Bird Count--just skill/effort at observing, identifying, and estimating counts. Birders largely ignore the common species during most of the year (though I find robins highly photogenic), but for the CBC census they all get counted. (For example, the 2022 Glen Helen CBC in Yellow Springs tallied 243 starlings, 158 robins, and 73 Carolina chickadees, among many other species.)
The real value in these censuses comes with the long term accumulation of data; the details of individual count variables gets washed out in the accumulated data, and important trends become visible. A corollary is that these counts really become worthwhile if there's a pretty robust commitment to do them over space and time.
Here's an example for butterflies in Ohio:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0216270
For birds, if you're interested, some of the guidelines for the CBC are covered here:
https://www.audubon.org/answers-your-top-questions-about-christmas-bird-count
and a guide to setting up a CBC here:
http://home.pacifier.com/~mpatters/cbc/acbc.html
I really don't know if something like this is feasible for odonates. The date and geographic range data already are really valuable; I just ponder whether there's a way to add more quantitation.
Mike makes some good points. In addition, I might add that a few of our rare species might be OVERrepresented because of the the effect of people looking for them in known habitats - Cedar Bog - or are seeking them out at known locations - Paiute Dancer, Jade Clubtail, Duckweed Firetail. Meetings also play a role; at the 2004 OOS meeting a Green-Faced Clubtail was caught and posed. John Pogacnik and I took almost identical images of it; John's photo is in Dennis Paulson's book and there must be a dozen people who also have images of it - I can think of numerous other examples. The Duckweed Firetail is a different example; as best as I can tell there was but a single male at the site, but a number of us went to photograph this rare specimen.
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