2025 City Nature Challenge Bioblitz

A Participant’s Perspective

Sharon Moore

The City Nature Challenge (CNC) is an annual international competition between municipalities to document their local biodiversity through the efforts of citizen scientists. It was created in 2016 by the community science staff at the Natural History Museum of Los Angeles County and the California Academy of Sciences for the first-ever Citizen Science Day. The goal was to “capitalize on their home cities’ friendly rivalry and hold an event around urban biodiversity” (https://www.citynaturechallenge.org/about). The eight-day competition successfully engaged residents and visitors in documenting nature and gaining a better understanding of their urban biodiversity.

The CNC has quickly grown into a truly global event, with over 400 cities across more than 40 countries taking part (BioScience, Volume 74, Issue 4, April 2024, Pages 290–299). From the Americas to Australia, the “bioblitz” is now conducted annually over four days in the spring, with cities worldwide striving to see who can make the most observations of nature, find the most species, and engage the most people.

The CNC is one of the projects that Texas Master Naturalists can participate in to earn volunteer hours. As a Hays County Master Naturalist, I’ve participated in two CNC bioblitzes here in Hays County, which is considered part of the Austin Metropolitan Area. Both times it was work—and I loved it. It’s a wonderful way to get outdoors during the height of wildflower and migratory bird season, with the added satisfaction of knowing you’re helping to expand our knowledge of the planet’s biodiversity.

Central Texas Wildflowers Photo courtesy Sharon Moore

This year, from April 25–28, I joined other citizen scientists to photographically or acoustically document as many local plant and animal species as possible. I did this as a team with my husband, who provided much-needed technical support. The CNC can be done independently, as we did, or as part of an organized group, if one exists in your area.

Prepare yourself for the challenge!

To effectively participate in the CNC, there is some “prep work” and a few simple rules to follow. Observations should be primarily of wild living things—plants, animals, fungi, lichens, even microorganisms. They can be made photographically or acoustically, and the location of each observation must be noted. The photos, recordings, and their locations are then uploaded to iNaturalist. This can be done via the iNaturalist app or their website. Once uploaded, there are four additional days for enthusiasts and other citizen scientists to confirm the initial species identifications made through iNaturalist. This is another way Master Naturalists can earn volunteer hours—by helping verify those initial IDs.

Texas Spiny Lizard (*Sceloporus olivaceus*) Photo courtesy Sharon Moore

I found the prep work really vital to successful observation and to increasing the number of observations that can be made within the bioblitz timeframe. The first step is getting an iNaturalist account. I recommend downloading the iNaturalist app as well. It’s important to familiarize yourself with how both the app and website work. The app makes it easy to upload photos or recordings taken with your smartphone, and often the location is automatically logged if you’ve enabled that in your phone settings.

The downside of the app can be your phone camera’s limitations. Mine doesn’t do macro photography well, and sometimes a telephoto lens is needed for distant subjects—so this year I used a digital SLR camera instead. I downloaded the photos from the camera to my laptop, which allowed me to screen them and improve clarity if necessary. To make an individual observation I uploaded those photos and their locations manually into the iNaturalist website. This is a more complex process than what is automatically done by the phone app. So keep good notes about where you took that great picture of a bluebonnet, because metadata can be lost when transferring files between devices. Was using this method worth it? I say, yes, when I look back at the number of blurry pictures from my previous bio-blitz.

It helps to practice with your camera a few days before heading into the field, especially if you don’t use it regularly. That way, you won’t waste time fumbling with settings or focus. To increase the likelihood of successful species identification, try to get multiple photos at different scales. For example, with plants, take a picture of the whole plant, then take close-ups of leaves, flowers, seeds, stems, bark, or other identifying features.

You may need a prop such as a blank sheet of paper to provide contrast, such as in the photo below of the turkey tangle frogfruit.

Turkey Tangle Frogfruit (*Phyla nodiflora*) Photo courtesy Sharon Moore

It’s more challenging to get multiple in-focus shots of mammals, birds, or insects. But try your best to capture at least a couple of photos that show distinctive features like coat or carapace patterns, eye stripes, wing bars, or antennae.

Plains Bee Assassin *(Apiomerus spissipes)* Photo courtesy Sharon Moore

It’s not forbidden to include photos of garden plants or other non-wild organisms, but be sure to mark those as "Captive/Cultivated" before uploading. Since the goal is to focus on wild organisms, avoid pictures of dogs, cats, livestock, roses, petunias, etc. Of course, in our neighborhood, it’s hard to say whether the white-tailed deer are wild or semi-domesticated.

White-tailed Deer *(Odocoileus virginianus)* Photo courtesy Robert Moore

Observations can be made in the countryside or in urban settings—even in your own backyard. My first bioblitz year, I took many of my pictures at Purgatory Creek Natural Area in San Marcos. This year, I spent part of my time in my neighborhood and yard—low-hanging fruit. My main focus however was wild plants, since I can’t resist spring wildflowers, so I spent most of my observation time on the side of a Hays County country road.

I made sure to wear sunscreen, a hat, bring plenty of water, and keep a sharp eye out for snakes. To avoid chiggers, I sprayed my pant legs and changed out of field clothes to shower as soon as I got home. (TMI, perhaps—but it worked!) That roadside turned out to be super rewarding because of the diversity. I found some plants I’d never seen before, such as the trailing rhatany below.

Trailing Rhatany *(Krameria lanceolata)* Photo courtesy Sharon Moore

I began uploading observations by the end of the second day, which I highly recommend. Sorting through all those photos can become overwhelming. Uploading earlier can also help avoid duplication. I found I had photographed the same species more than once—not always a bad thing, but the goal is to find as many different species as possible. Early uploads also make it easier to correct missing or incomplete metadata.

As I entered each observation, the iNaturalist tool suggested an ID based on my uploaded photo. Sometimes the family, genus, or species was obvious—other times, not so much. If it is a species found commonly in the area then it’s a pretty safe bet, and I agreed with the tool 95% of the time. There were only a couple of instances where the suggested ID was clearly off, and a different photo led to a better match. When uncertain, you can enter the family or genus and hope a verifier helps narrow it down. It’s helpful not to get hung up on achieving “research grade” status, which requires at least two community confirmations to the species level. Some insects, spiders, fungi, and plants can’t be identified down to the species level by photographic evidence alone.

Goals for next year…

I plan to participate in the CNC again next year and have a few goals. First, to double my number of observations. Lessons learned: practice more with my camera and with the iNaturalist website ahead of time (I could have done better with that). Also, don’t overlook common plants and animals in my yard and neighborhood. I was so focused on finding rare or unusual species that I missed a lot of easy observations. Still, my husband and I did catch a few nice moments—like the fox squirrel and bluebird pictured below.

My second goal: help the Austin Metroplex move up in the contest rankings. This year—like in previous years—we were clobbered by the San Antonio Metroplex, which came in second globally behind the La Paz Metropolitan Area, Bolivia, for most observations (https://www.citynaturechallenge.org/current-results). Austin placed thirteenth, and I know we can do better.

My third goal: capture more amazing wildlife photos. I only got one shot of this cruising Common Buckeye—but it was a keeper!

Common Buckeye *(Junonia coenia)* Photo courtesy Sharon Moore

Other sources:
Educator Guide: Using iNaturalist with Students.pdf

Be Sure to Make Useful Observations

A Participant’s Perspective

Birds, Binoculars, and Big Smiles

The City Nature Challenge Wrap-up