In late March, scientists launched a new field experiment at the ARM Facility’s Southern Great Plains (SGP) site in Oklahoma to collect data about the flight preferences of migrating birds. For the next two months, a field team led by University of Oklahoma is conducting the Spring 2014 Nocturnal Avian Migration Experiment, using a pole-mounted passive acoustic array—an animal vocal recording and tracking system—accompanied by a forward-looking infrared (FLIR), or night vision, camera.

Researchers will analyze data collected from these instruments along with continuous measurements from the dense SGP instrument suite, particularly biological signals hidden in datastreams from ARM cloud and precipitation radars. These data will allow researchers to study a range of small-scale questions related to aerial habitats, and provide an expansive look into long-term changes in migration patterns in the Great Plains.

Clutter to One, Treasure to Another

Radars at the ARM sites send a beam of energy into the sky. Signals that bounce back off of microscopic ice and water particles in clouds give scientists information about that cloud. The signals also bounce off of bugs, birds, and other flying critters. This “clutter” in the radar datastreams actually contains some of the highest quality small-scale ecological measurements pertaining to airborne organisms over North America.

Using the passive acoustic array, developed and tested at the University of Oklahoma, the team is collecting the nightly recordings of the calling behavior of birds within a range of 500 meters of the SGP site. All of the data is logged to internal memory cards and will be processed at the University of Oklahoma. The team will use a custom algorithm to determine the abundance of calls, 3D position of individual birds, and species classification of the detected signals.

In addition, the team will run the FLIR thermal camera over five selected nights to provide additional validation of the identity of the organisms in the path of radar beams. These data will give quantitative migration passage rates, headings, and identities of the organisms appearing in the radar datastreams.