Carlos Avery Story of the Day
Post date: Jun 29, 2020 5:25:20 PM
With Cedar Creek Ecosystem Science Reserve still closed to all but essential research, members of the Minnesota Wildlife Tracking Project moved our Summer Survey to the nearby Carlos Avery Wildlife Management Area. Over the weekend of June 13 & 14, socially distanced trackers explored roads and trails in the WMA and brought back our stories to share. Here are a few highlights. You can see all of our observations from the weekend here on iNaturalist.Perhaps the largest surprise of the weekend was the relative lack of mammal sign. In a typical survey at Cedar Creek, our teams often return with scores of observations of mammal tracks from more than a dozen different species. Over this weekend, we collectively identified the tracks of just 6 species of mammals, plus the sign of five more. For half of those species, we made only a single observation. Those observations included a single fox scat and single coyote scat, as well as these fresh weasel tracks that were disappearing quickly in the wind—suggesting that the weasel had come through only a few minutes before this observation was made. As usual, our trackers located the digging signs of local fossorial mammals. We can identify pocket gopher activity like this to species, because the plains pocket gopher is the one member of the family in this part of the state. But it is not so easy to identify mole tunnels to species. We have both eastern moles and star-nosed moles around the metro area. We have similar challenges identifying other tiny mammals, such as voles and shrews, from their tracks and sign. For positive identification, we usually need a skull or a carcass. On this survey, we turned up this masked shrew corpse. Since shrews scurry about much like voles, but are apparently much less appetizing, it is not rare to find nearly intact bodies—perhaps discarded by a disappointed predator.
The one mammal that we did find abundant tracks for was the common raccoon. In particular, we found several spots where raccoons were raiding what appear to be bullsnake nests. We had found a dug-out snake nest once before on a survey at Cedar Creek. This weekend, we located more than a half-dozen. Bullsnakes are common in this area, as evidenced by the bullsnake trails we found crisscrossing many of the roads we explored. According to Moriarty & Hall's “Amphibians and Reptiles in Minnesota,” June is nesting season for bullsnakes and it seems that the raccoons were making quick work of these newly laid eggs—although in one of the excavated nests, we found an egg that was still intact. Our team also recorded the tracks and sign of quite a few birds. Our findings included common and familiar species such as sandhill crane and American crow, but also a bank swallow nesting colony. As their name suggests, bank swallows historically formed their nesting colonies where erosion has carved sheer faces into the sandy banks of streams and rivers. The species common name, and Latin name Riparia riparia, recognize these riparian roots. Over the past century, the species has broadened its habitat to include vertical road cuts and the edges of gravel and sand mine pits, like this one. The nesting holes themselves are similar to those of kingfisher, but appear more oval. They are distinctly wider than they are tall and, like kingfisher burrows, have two "tracks" along the base where the birds feet appear to shuffle as the enter and exit. Finally, our surveyors ran across a huge diversity of insects and insect sign. Most of us of course are not entomologists, or even bug collectors, so our ability to interpret what we are finding is modest. But one sighting that is worth sharing is our first confirmed sighting of antlion traps. Antlion larvae excavate conical traps in sandy soil where they capture unlucky ants and other hapless critters. They are common, wide spread, and a favorite question on CyberTracker evaluations. But they are something that our trackers rarely encounter here in Minnesota. On a couple of occasions, we have found conical depressions in the sand at Cedar Creek that looked like antlion traps, but we were unable to locate the larvae to confirm this. On this occasion, there was no doubt. We watched the larvae excavating traps and drag an ant down into the sand. We also dug one out to get a close look at this stuff of insect nightmares. It has been a treat to explore Carlos Avery during these months when we are unable to track at Cedar Creek. But we are looking forward to returning to our usual routes before long. The University of Minnesota plans to resume in-person instruction in the fall, and we have confidence that we will be able to hold our Fall Survey at Cedar Creek – perhaps with some modifications. Mark your calendars for the weekend of October 2-3 and stay tuned for updates as the start of the school year approaches.