Monday, May 4, 2009

Owl's White Patch Aids Visual Communication

Posted by Kirk Mona
I work with a captive Barred Owl but from time to time I get to see some of my peers in the field do programs with Great Horned Owls. Have you ever watched a Great Horned Owl call? It always struck me that they have this white throat patch that really puffs in and out when they call. If you've never seen it in action, watch the video below.



In a new research paper published recently in the journal PLoS ONE, scientists Vincenzo Penteriani and Maria del Mar Delgado of the of the Estacion Biologica de Doñana in Spain believe that the white patches aid owls by adding a visual component to calls. Visual? This might seems strange for a creature many people consider nocturnal but in reality, owls are crepuscular meaning they are most active at dawn and dusk. There are great advantages to being crepuscular if you are an owl. It is dark enough that you can hide from prey but still light enough that you can see them. According to Penteriani and Delgado, there is enough ambient light at twilight to make the white throat badge useful as a communication tool.


Numerous studies have sought to explain the amazingly widespread phenomenon of the so-called dawn and dusk chorus, i.e. the sunrise and sunset peaks in bird song output... To date, the majority of studies on this topic have focused on songbirds, which might contribute to a biased view of bird vocal communication. It seems likely that if multiple hypotheses are necessary to explain songbird dawn and dusk choruses, many others could be necessary to explain the functions of vocal signaling at sunrise and twilight in other bird families. Until we gain a better understanding of daily patterns in signaling by as many as possible bird families, we will not completely understand why birds sing. In addition, we need to examine nonvocal means of communication and how they might be associated with vocalization. It is well-known that diurnal birds use an astonishing variety of color signals to visually communicate: did crepuscular and nocturnal species find a way to communicate by visual signals? Our present study shows that crepuscular and nocturnal species appear to have evolved white patches that, shown in association with vocal displays, allow them to communicate in dark surroundings.
Their study focused on the european cousin to the Great Horned Owl, the Eagle Owl. Get your geek on and read the entire research paper online titled, The Dusk Chorus from an Owl Perspective: Eagle Owls Vocalize When Their White Throat Badge Contrasts Most.

~Kirk

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