Sound signals provide important ways for birds to communicate. Playing a recording of a bird’s song may attract the attention of a female and usually attracts the attention of males, intent on driving away the intruder. Alarm calls may attract a diverse group of birds, congregating to mob the threat that caused birds to issue the alarm.
The use of playbacks of recordings of those sounds has been a powerful tool for ornithologists for decades. Playing vocalizations at different times of the day or at different times of a season helps us understand the function of different sounds. Playbacks can be used to map the boundary of a bird’s territory. The ornithologist walks toward a singing male. The male will usually ignore vocalizations of a neighboring male until that male (or the playback) crosses into the first bird’s territory. In this fashion, it is possible to map the boundaries of a territory with amazing accuracy.
With the advent of smartphones and bluetooth technology, it is easy for a birder to play bird vocalizations to attract birds for a closer look. There are lots of apps of bird sounds available for smartphone use. A small bluetooth speaker emits a surprisingly loud sound, amplifying the relatively weak smartphone speaker. These playbacks are highly effective.
The use of playbacks has some ethical implications. A male bird’s stress hormones increase immediately after hearing the sound of a putative intruding male. Birds become agitated, increasing their metabolism. They must increase their food intake to replace those calories used in response to a perceived threat. The use of alarm calls has an even stronger effect. Playing a recording of chickadees mobbing an owl or the vocalizations of a Northern Saw-whet Owl attracts numerous individuals of multiple species.
I do not use playbacks when I am birding by myself. When I lead a field trip, I occasionally will judiciously use playback to attract hard-to-see birds. My logic is that the minute or so of stress on a bird from hearing a playback allows everyone in the group to see the bird. Spending ten minutes of more following the bird around to allow everyone to get a look may be more stressful on the bird. I never use playback in a frequently birded area because other birders may be using playbacks at that site.
Other birders use playbacks often. One example is Birding Bob, a New York City birder who plays vocalizations often and at high volume in places like Central Park. The New York Times recently posted a video op-ed of Birding Bob with commentary from several other birders. The video provides a balanced look at the pros and cons of using playbacks. You can see the video by clicking here.