The Texas night sky is full of life. On almost any night of the year, there are insects from ground level up to over a mile high. And where there are insects, you’ll find bats trying to catch them. For ecologists, however, this is a very challenging place to work. Studying tiny animals so far overhead is very difficult! As a result, clever scientists are adapting some amazing technologies to allow us to “see” what’s going on up there.
This equipment from Vogelwarte, the Swiss Ornithological Institute, is a specialized radar that “sees” animals flying overhead. It looks straight up and can discriminate targets as small as a large moth at altitudes from 50 meters high up to over 2500 meters (over a mile!) high. It was designed to study bird migration and can recognize birds and insects and tell how high they are, which direction they are flying, and how fast they are going. We have temporarily installed it near Seguin, Texas to train it to recognize bats. Because this site is close to the largest Brazilian free-tailed bat colony in the world, it will record echos at night of hundreds of bats flying overhead. The blue image above is a visual snapshot of what the radar saw over time at this site on a recent night. The numbers on the left are the altitude in meters – so this shows what the radar saw from 200 up to 800 meters overhead (that’s 650 feet up to 2500 feet). The green circles over larger swoops are probably bats, and the red crosses over smaller swoops are insects. There are surely insects higher than appear here, but the radar doesn’t see smaller insects much higher than 200 meters or so. Because this is Texas and everything is larger and more abundant than other places, we’ll have to do some work to calibrate the readings. Once we have a better idea of what the targets actually are, I’ll explain more about how to interpret these diagrams in a future blog post.
This data will help scientists to distinguish between birds and bats at sites anywhere else in the world. This is a collaborative project involving Cornell University, the University of Massachusetts, the Swiss Ornithological Institute, the University of Tennessee, and other research groups interested in applying advanced technologies to studying animal migration.