A studio for bird study

Tag: owl

April 11, 2015

Female Barn Owl “Spottiness” Signals Genetic Quality

by Bryce W. Robinson

2015-03-19 16.34.51

To begin, I should have illustrated the frontside of this Barn Owl to illustrate the concept I’m about to present. I did not, however, have “spottiness” in mind when I began the illustration, so I decided to illustrate the backside. I find the back patterning mesmerizing.

So, for the concept you’ll just have to imagine the frontside of this bird, being spotted throughout.

Ornamentation in birds is generally considered a male’s way to communicate their quality to females. A more ornamented, vibrant, decorated, etc. male is generally considered higher quality, thus driving selection for particular traits (Peacock is an easy example, but think about birds like the Greater Sage-grouse as well).

Studies supporting this theory have generally focused on males, and for good reason. Males tend to be the showier sex. But, what about species where females exhibit unique markings?

Barn Owls are one species where the female shows more markings (spots) than males. Additionally, studies support that female Barn Owls are not the choosers in breeding, as per usual. Because of these reasons, Roulin et al. (2000) decided to test the theory that heavier spotted females were of higher quality (tease out the mechanisms of spottiness). They hypothesized that females with more spots also had higher levels of specific antibodies important for parasite resistance.

Their study looked into immunocompetence of offspring. They found support for the idea that heavier spottiness communicates immunocompetence, but also may be a “heritable signal of parasite resistance”. This is important for Barn Owls, as they nest in cavities and tight spaces. I remember a few weeks ago I went with a peer, Tempe, to check on a Barn Owl nest for her Master’s Project. The box held four owls (lower than normal), and was full of feces and dead animal remains. In such situations, parasites and all sorts of things may run rampant. Having higher resistance then becomes advantageous, and ways of communicating such resistance will then be selected for and prevail. Makes sense (eureka?).

Literature Referenced:

Roulin, A, T. W. Jungi, H. Pfister, and C. Dijkstra. 2000. Female Barn Owls (Tyto alba) Advertise Good Genes. Proceedings of the Royal Society B-Biological Sciences 267 pp. 937-941

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February 1, 2015

Barred Owl – Out of Range but Seemingly Comfortable

by Bryce W. Robinson

 

Around the turn of the year a Barred Owl – Strix varia, was reported in Boise, Idaho. The owl has been seen regularly for the past month. Barred Owls occur in Boise once every few years as vagrants from somewhere unknown. This Barred Owl showed up in a city park on the east side of town, only about a mile from the foothills. The peculiar part is that the park is adjacent to the Boise River, a large wooded area, and acres of open field. Instead of occupying these more wild, less human areas, the owl has chosen the back yards adjacent to the park to roost. The bird hunts the park edges and greens at night, apparently having loads of success. This behavior is a testament to the hardness of this species against human disturbance. It is one of those few species that seems to do well with the world we are creating.

I took the video above a few days ago just before sunset. The owl was alert, no longer snoozing. The most interesting thing about the video is the birds behavior coupled with the anthropogenic noise. In the clip you can hear a man playing fetch with his dog, someone closing a house door, and many other human sounds typical of urban living.

Why is this Barred Owl able to tolerate a lifestyle like this, yet other species are so sensitive to disturbance? The Barred Owl’s closest North American relative, the Spotted Owl, is certainly having a hard time with the way we are changing its world. These types of questions are worth entertaining as more and more we change the world around us, better for some but certainly not for all.

 

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October 8, 2014

Burrowing Owl Illustration

by Bryce W. Robinson

Burrowing Owl - Athen cunicularia. 11 x 17" prismacolor on bristol

Burrowing Owl – Athene cunicularia. 11 x 17″ prismacolor on bristol

When I first began illustrating birds seriously almost three years ago, I spent the majority of my time on owls. For whatever reason, I was fascinated in the way their faces translated onto both canvas and paper. I remember when I realized the power that the eyes have for communicating the spirit of life within a creature. The exercise of illustrating owls taught me the importance of light and detail in the eyes of birds, especially raptors.

In the past I was focused on illustrating the face and busts of birds of prey. I stayed away from illustrating the full body of birds due in part to my fascination with the face, but also because I felt that I couldn’t create a proper and natural bird. Now I’ve started a campaign with myself to overcome my weaknesses and illustrate birds as a whole, either perched or in flight. While the exercise is to properly portray a bird in whole, I’ve made it a priority to take the lessons I learned from illustrating a birds face and invoke the same sense of life and attitude in the full-bodied bird.

Creating images of living creatures has more to it than I’ve ever thought. I see incredible paintings of Gyrfalcons in flight pursuing prey, or a Great Blue Heron stalking something in shallow water, and I can’t help but marvel at the mastery the artist holds over both their medium and their subject. I hope to reach even a fraction of the ability of some artists, but at the same time I’ve realized that perhaps the process is more enlightening and more worthwhile than the product. In the end, I’ll understand birds to a greater degree simply because I have put energy and focus into their details, and attempted to communicate their life and spirit through my own creative ability.

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April 4, 2014

A Communal Roost of the Great Horned Owl

by Bryce W. Robinson

 

I’d like to share this video of a solitary roosting Great Horned Owl to introduce a story and celebrate a career goal accomplished for both Caitlin Davis, and myself.

In December 2012, Caitlin and I were conducting Golden Eagle surveys in the west desert of Utah. One evening on our survey route near the border of Nevada and Great Basin National Park, we came upon a roosting pair of Great Horned Owls. These owls sat in a small string of trees about 30 m in length. Soon after we discovered the roosting pair, we noticed an additional four owls in the same tree line. A total of six owls sat together in close proximity, and soon after we counted the birds, I knew the significance of what we had found.

Because I knew that Great Horned Owls are extremely territorial, I looked into the literature hoping to find any reports of similar roosting behavior. After what seemed to be an exhaustive search, I had found no reports of any communal roosting behavior for the Great Horned Owl, or any other Bubo species.

I discussed the idea of reporting the findings with Steve Slater, Shawn Hawks, and Markus Mika at HawkWatch International. They were supportive of the idea, so with little hesitation I wrote a short report of the roost and submitted it for publication to the Journal of Raptor Research.

The report was accepted, and has now been published in the latest issue of the JRR. Caitlin and I are extremely grateful to everyone who helped us get the word out in the proper fashion by talking out ideas, and revising the manuscript. It was a fun process, and I look forward to repeating it again in the future.

Read the article here:

Robinson, B.W. and C. M.  Davis. 2014. A communal roosting of the Great Horned Owl (Bubo virginianus). Journal of Raptor Research 48(1) 88-89

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