Dam Bioblitzing: What Lurks in the Marsh


In theory, conducting a bioblitz was going to be a simple enterprise. I would go to one of my chosen spots, count the organisms as I went along, noting them in my book and, if possible take a photograph. I figured the two places I'd chosen would be relatively barren. In the tall grass prairie (especially one that has been mowed) you expect lots of grass, the occasional shrub or succulent, and the standard plains fauna, mostly passing birds and a profusion of prairie dog mounds. Site A is one of my regular haunts, and I knew I'd spot, at best, some waterfowl or wildflowers there.


I chose Site B sort of randomly. I wanted a place along Big Dry Creek (the main outlet for the dam) that was easily accessible and downstream from Site A. According to Google Earth, Site B was the first place fitting the description that wasn't adjacent to someone else's backyard. While I've lived near the creek for a good part of my life, and have visited many spots along it, I had only visited that particular spot once, long before: I was getting my senior picture taken for the high school yearbook, and the photographer wanted an outdoor shot. It ended up being the one I chose; I remember telling people, "yeah, it turned out great, considering the background is just some ditch."

Well... that "just some ditch" downstream from the dam was hiding a few secrets. I drove by the location with my son. He saw a cool-looking bridge and begged to join me. I figured I wouldn't have much to do, expecting a relatively dry location, and agreed to bring him along. We drove in, parked, and got out of the car. Roland ran off to "bioblitz the bridge" as he put it. I just stood there, looking at the site, dumbfounded.

"Well, I'll be dammed!" I cried, even though it was actually the creek that was dammed. Right in front of my parking space, a large beaver dam rose from the creek bed. Behind it, the land in the center of an oxbow was hidden beneath a grand marsh, teeming with life. So much for a quick count.


Roland was watching a flock of blackbirds dart in and out of a shrub by the bridge. The shrub was growing out of the mud, oozing from an older, abandoned beaver dam. The birds were quick, dashing to the next bush before I could take a picture. At first, I thought they were red-wing blackbirds, which are common in this area. Then I noticed they were jet black with shiny blue patches on their heads. I've yet to figure out what they were... they seemed too small to be grackles. Whatever they were, there were at least 30 in the flock that fled.

I realized then, with an eager (and noisy) young boy along, I was not prepared to make any sort of official count. At least I could establish what it was that I would be counting. The flooded creek beds turned out to host a wise variety of birds. We spotted several mallards, all male, and a few Canadian geese. The best avian discovery of our journey, however, came once we passed a third beaver dam.

Roland ran down the trail a bit, while I paused under a small grove of tall cottonwoods to rest and survey the marsh. Out of the corner of my eye, I saw something move in the trees above. I looked up, and was suddenly startled. "What's a penguin doing in the tree?" I thought. It wasn't a penguin, exactly, and indeed, couldn't be. But it was a bird I'd never seen before. As I reached for the camera, I noticed the strange bird had a mate, which was more clearly not a penguin. Of course, as soon as I saw the birds, the birds saw me.


I snapped a few pictures (see the link below for more) just in time to see them take flight around the wetlands. As soon as their wings spread open, I knew, without a doubt, that I'd stumbled onto a heron roost. The magnificent creatures circled the area, and returned to the trees overhead. In flight, they resembled the great blue herons I've seen all around the Front Range, but without the long, curving necks.

I eventually realized they were black-crowned night herons, (Nycticorax nycticorax) a species I'd read about, but never seen. These stealthy birds usually hunt during the evening or early morning. (I must have caught them napping.) When it is dark enough, they'll lurk on a branch near the water, waiting for an unsuspecting victim to pass. The hapless frog or fish (or worm or lizard or bug or floating garbage--these herons aren't picky) never knows what hit them.

I knew I would have to return in the early morning if I wanted to catch these beautiful birds in action. The same went for the industrious mammals responsible for this lush habitat, the beavers. Nearby, another type of resident mammal was making its presence well known:


On the south side of the creek, there is a large field, filled with prairie dog (Cynomys ludovicianus) mounds. This little guy's mound was on the north side, however, not far from the parking lot. It is normal for the sentry's mound to be a short distance from the rest of the colony, but across the creek seemed a stretch. I wondered if they could scale across the beaver dam. The rodent's barks as I passed assured me that no matter where I walked, I would be too close to his territory.

Since my young helper was getting restless, I didn't get the chance to log any flora at the site. So, our bioblitz count for the weekend was low, even if we had discovered a highly diverse habitat. We saw, but didn't necessarily count.

Wildlife Count

Kingdom: Animalia

  • Phylum: Chordata
    • Class: Aves
      • Order: Anseriformes
        • Family: Anatidae
          • 2 Branta canadensis (Canadian Goose)
          • 4 Anas platyrhynchos (Mallard)
      • Order: Ciconiiformes
        • Family: Ardeidae
          • 2 Nycticorax nycticorax (Black-Crowned Night Heron)
      • Order: Passeriformes
        • Family: ??
          • An uncounted flock of unidentified blackbirds
    • Class: Mammalia
      • Order: Rodentia
        • Family: Sciuridae
          • 1 Cynomys ludovicianus (Prairie Dog)
  • Phylum: Arthopoda
    • Class: Insecta
      • Order: Lepidoptera
        • Family: ??
          • 1 unidentified butterfly

Next time, I'll get an official count, including the number of prairie dog mounds, beaver dams, and trees, as well as some representative sections of wildflowers, insects, and more. The same goes for Site A at Standley Lake. I'd hoped to get out and do a little there today, but it has been blowing wind and pouring rain since I woke up. The rain is threatening to turn into snow. I'm really enjoying this project, but I can't say I'm devoted enough (or prepared) to bioblitz in a blizzard. Hopefully, it will blow over soon, and I'll be back, with more. To see more photographs from our excursion, or to see exactly where they were taken on the National Wildlife Week Bioblitz Map, check out the page on Flickr. While you are there, check out what others are finding in their bioblitzes.

All pictures were taken by the author.


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Ditto. What a beautiful bird.

I'm jealous of you and Bev. I wanted to head out to Cranesville Swamp sometime this week, but I'm buried under loads of physics homework.

I can really pinpoint which is the biggest crowdsourcing website (in terms of brand recognition). There are always seem to be a new one popping up which I've never heard. This time it's Crowdflower. The learning continues...