Screech Owling 101
Text and Photography Copyright Dr. Peter May
Many species of birds, particularly among the passerines, engage in a type of anti-predator behavior loosely known as mobbing. Because these behaviors can often be elicited by auditory cues even in the absence of a real predator, they provide the bird photographer with a tool to obtain photographic opportunities that would be virtually impossible in any other way. Birdwatchers have known about and used owl vocalizations for years to attract and view shy birds. I believe that most people will be able to make better use of this technique if they understand something of the natural history and adaptive significance of the behavior, so I'll begin with a brief overview of mobbing behavior, and follow that with specific hints and suggestions for using this behavior to increase your bird photography possibilities.
This term refers to a variety of behaviors in which a prey species locates and approaches, and in some cases physically attacks, a potential predator, particularly when the predator is not an immediate threat. Whether it be crows harassing a red-tailed hawk, a mockingbird dive bombing the neighborhood cat, or a flock of passerines flying hundreds of yards to seek out a vocalizing owl, all presumably function somehow to decrease the probability that the predator will make a meal out of the mobber (or his relatives) at some future date.
Many species of passerine birds (and some non-passerines, such as woodpeckers and hummingbirds) mob owls found in the open during the day. The urge to locate and somehow interfere with the predator is so strong that many species will respond to owl vocalizations alone, and travel significant distances to find the calling owl. Once located, the mobbing species may show a variety of different behaviors, ranging from simple approach to various distances (many warblers), approach with vocalizations (wrens, titmice, chickadees), and direct attack. Ornithologists have never resolved exactly what the benefit of mobbing is to the species involved, but hypotheses suggest several possible functions, including a) injury of the predator (rare), b) driving the predator away, and presumably reducing the chances of future attack, and c) education of naïve, young birds on how to recognize specific predators. Key to most mobbing behaviors, though, is that they occur in response to predators that are not an immediate threat. Owls, for example, are primarily nocturnal, ambush hunters. They are not capable of attacking and capturing small, agile passerines that are aware of their presence and are flitting actively all around them. Predators that are an immediate threat (Accipiter hawks, for example), are treated with an entirely different set of behaviors and vocalizations than are owls (retreat to cover, crypsis, non-localizable alarm calls). Because mobbing behavior confers no immediate benefits to the mobbers, it seems often to be a relatively low-priority behavior that the mobbing species engage in only when other, more pressing biological demands such as hunger, mate attraction, or taking care of offspring do not require the immediate attention of the birds. This is probably why response to screech owl vocalizations is so variable and unpredictable, and of such short duration when it does occur.
Some national parks and other wildlife refuges ban the use of any recorded vocalizations to attract birds, so be aware of the regulations wherever you are. Overuse of tape playback to attract birds can be detrimental to the survival and reproduction of some species by preventing them from devoting full attention to other biological demands, such as feeding their offspring. However, I don't think this is a concern when using screech owl tapes. Playback of the species-specific territorial song of many species during their breeding season will attract territorial males to the source of playback for up to hours at a time, if the person playing the tape is persistent. Response to screech owl tapes is entirely different - the birds often don't respond at all, and when they do, even the most vigorous responses wane and disappear within 10 minutes or so, as the birds drift away to resume their other activities once they discover no predator producing the vocalizations. It is virtually impossible to immediately attract those birds again. Essentially, the behavior of the birds regulates the effectiveness and impact of using owl tapes.
One negative impact that can result from use of owl tapes is attraction of other predatory birds to the mobbing flock. On probably half a dozen occasions, I have seen sharp-shinned hawks burst into the middle of a mobbing flock and attempt to pick one off. Most of these attacks have been unsuccessful, but be aware that you are sometimes producing a concentration of prey that can attract predators. I've seen more birds killed by hawks at bird feeders than in mobbing flocks, though. It's a dangerous world out there for a dickey bird.
The equipment used can be as simple or sophisticated as you like. Outdoor suppliers (such as L.L. Rue, Cabela's) provide high-fidelity playback equipment with amplified speakers to increase sound quality and broadcast range, but you can obtain excellent results with a small, handheld cassette recorder. I use a portable recorder made by GE that is about the size of a field guide and sells for $20 at any Wal-Mart or K-Mart. When I call from a car, I plug it into a small, amplified speaker from Radio Shack (~$15) that runs on 4 C batteries. The few microcassette recorders I've tried have had insufficient volume output to be effective.
The tape should contain at least 5 minutes of continuous owl vocalization. You don't want to have to stop and rewind the tape in the middle of a mobbing episode, as activity levels are high and photography of the frenetic birds will require all of your attention. Endless loop tapes are ideal. A 30 second loop tape will contain 2 to 3 bouts of vocalizations recorded from a typical bird song record or CD. The vocalizations can be separated by slight pauses or more or less continuous. It doesn't seem to affect attractiveness. Sound quality doesn't seem particularly critical either; tapes recorded through the built-in microphone of a portable cassette recorder work fine. Try to record the tape at as high a volume as possible without distortion to maximize auditory range.
Eastern Screech Owls have two primary vocalizations, a descending trill and a monotonic trill. Both are present on some commercially available bird call recordings. The descending trill is thought to be a territorial defense call used mainly in late summer and fall, while the monotonic trill is considered a nest-site advertisement and family contact call, and is heard more in early spring and summer. I have used each of these calls alone, and interspersed, and I seem to get better response when both calls are present. All variants work well, however.
Some mobbing species are highly vocal, and produce similar sounding buzzy, scolding calls (wrens, vireos, chickadees, titmice, kinglets, gnatcatchers). The presence of these alarm calls seems to enhance attraction of other species to the mobbing flock. These sounds are easily imitated by sucking air through pursed lips on the back of your hand (squeaking) or making pssssh sounds (pishing). Both techniques are used by birders to attract birds, and will work well even without owl vocalizations. Many birding supply companies sell small mechanical squeakers of wood and pewter that produce a variety of chirping and squeaking sounds. These sounds will also sometimes bring birds in closer than they would come with the owl tape alone.
The use of taxidermic mounts of screech owls or even simple model decoys may enhance photographic opportunities even more, as it would give the birds a specific focus for their attention. I've never tried either, but would encourage anyone interested to pursue it report on their results.
Some tips for maximizing your photographic opportunities with owl tapes.
Caveat - My experience is exclusively in eastern N. America, where the screech owl is a common and widespread resident. From reading the ornithological literature, however, it seems that mobbing behaviors by small birds, especially in response to owls, is widespread if not universal. My guess is that vocalizations of small to medium sized owls that are native to other areas of the world will elicit similar behavior among the birds there.
Dr. Peter May is a professor of biology at Stetson University in DeLand, Florida. An avid birder since his teenager years (before they were called "birders"), an entomologist/lepidopterist since about 1977 and a herpetologist since 1992, Dr. May resides in DeLand, Florida with his wife Deborah and their two sons, Sam and Benji.