Thursday, January 3, 2013

Barn Owl Coloration

 Blog reader John Foehner recently submitted the following comment on our blog article "Barn Owl Fun Facts: Part 1": “Great info!  Barn owls are one of my favorite birds. Here's a question for you that I've never had answered... Barn owls are beautiful birds with an awesome design on their light golden/tan/white feathers.  Why?  It doesn't seem to be used for camouflage and a largely nocturnal bird wouldn't seem to need special coloring for ID or courting?  Although most birds are pretty in one way or another, I can't figure out why barn owls look the way they do.  So, why? “
Just a few of the color pattern variations here at WBS--left to right are Moonshine, Farnsworth, Dawn & Abby
I’ll have to admit that even though I have taken hundreds of photos of the Barn Owls at WBS, I had simply taken their beautiful feather patterns for granted as just another part of what makes this species so fascinating. 

John’s question sent me into a fury of researching the whys and wherefores of Barn Owl coloration. 

There are approximately 35-40 known subspecies of Barn Owls--the exact number is arguable, depending on which expert source you are reading at the moment.  Since Barn Owls are found on every continent except Antarctica (and some islands), their territories sometimes overlap resulting in some sub-species that interbreed—thus the discrepancy in the number of listed sub-species. 
Our sweet little Tobin, a European Barn Owl, was so light colored that when viewed from below he might easily have been mistaken for a Snowy Owl
Among the multitude of sub-species there is a wide variety of differences in the coloration and shading of individuals—some being so light when viewed from below that they are sometimes mistaken for a Snowy Owl, and others having a buffy or beige coloring on the underside. 
Note how well this Barn Owl blends in when seen from above...even though this is not a natural environment
Even though Barn Owls are largely nocturnal, they are also crepuscular (active at dusk and dawn).  Hence the need for camouflage.  When viewed from above—they are universally a blend of dark grey/brown backs and wings.  This difference in coloration (light underside and dark backs and wings) is an example of “counter shading”—an adaptation used for concealment.  When in flight it allows them to take full advantage of the interplay between light and dark—enabling them to “disappear” as they change direction in flight, thus avoiding other predators who might be looking for a Barn Owl snack.

As a general rule, the white/light colored feathers on the breast are spotted—in some individuals the spotting is so light that from a short distance the breast appears to be solid white.  However, in other individuals the breast is heavily spotted.  The females are more heavily spotted than the males.
Abby is a good example of the heavier spotting on the female....
One of the most interesting theories that came to light in my research is that the spotting may indicate the quality of the female.  One study found that the more heavily spotted females get fewer parasitic flies and may be more resistant to parasites and diseases.  Also, in another experiment when some females’ spots were removed their mates fed the nestlings less often than for heavily spotted females.  As a general rule, most of my research sources concurred that it appears that heavily spotted females are healthier.
....whereas Moonshine is a classic example of the lack of spotting in the males
Another study showed that female Barn Owls with larger spots have a greater success in mating, whereas large dark spots on the breast appears to hurt male Barn Owls’ reproductive success.

And, finally, another study indicated that nestling Barn Owls frequently feed their siblings.  This behavior predominates in individuals displaying a female-like plumage trait (spots).

To see some of these color variations when visiting the World Bird Sanctuary be sure to check out the color patterns on the various Barn Owls on display.

Submitted by Gay Schroer, World Bird Sanctuary Volunteer/Photographer

1 comment:

Lemayrenee said...

Thanks Gay, lots of good information. It does make a lot of sense. I also wonder if the female being more spotted are more camouflaged when on her nest to better hide/protect the nest and the eggs/owlets. Whereas, the male, with the more brighter white breast stands out more to say this is MY territory look at ME Go Away! A male that blends into the background is not much of a deterrent.
I agree with you, Barn Owls are beautiful for what ever reason they are!!
Haha new word for the day crepuscular -active at dusk and dawn!