Within the past 50 years, the soundscape across the planet has changed dramatically. By soundscape I am referring to all of the sound combined across any landscape. From roads and highways to air traffic to resource extraction projects, our soundscape has been changing for the louder. My research focuses on how these novel soundscapes affect animals that historically have utilized quiet environments. My focal species is the Northern Saw-whet owl, an owl so specialized in detecting prey with hearing that it has evolved offset ears which are tremendously helpful for sound localization. In fact I've shown experimentally that these owls require no light at all to capture their favorite meal, mice.
This is the Northern Saw-whet owl, a small forest owl with a wide North American distribution. It also happens to be one of the most charismatic characters on the planet. To learn more about the saw-whet click here.
Here is the skull of a saw-whet owl. Notice the ear openings are asymmetrically placed in the head. This amazing adaptation has evolved independently in at least 5 genera of owls (Norberg 1977).
Fortunately for me, my research takes me outside. Here is the flight tent where we ran our experiments. The owls were captured with the help of the Intermountain Bird Observatory from the woods near the tent. Thirty-nine owls each got the opportunity to hunt mice in a variety of noise conditions ranging from 46-73 dB(A). What does it look like inside the tent?
Here is the bird's eye view. The owl (to my left in the picture) hunted mice while I experimentally altered the background noise level. I was not in the tent while this was happening, but we did filmed every hunting bout. We recorded everything with audio and video (our cameras are equipped with infrared capability so we are able to film the birds hunting in the absence of visible light). In this way we were able to quantify the effects of noise on an owl's ability to hunt.
Noise indeed impacted the owls hunting behavior. We ran a logistic regression to determine the odds of the owl orienting toward the mouse, striking, and capturing the mouse. This graph shows the probability of each of these behaviors as a function of noise.
Thanks to Neil Paproki and Ashley Jensen
for the wonderful owl picures.