Gyrfalcon T-shirts
by Bryce W. Robinson
We have Gyrfalcon T-shirts for sale on the ornithologi`art shop until April 20th. Click the photo or follow the shop link for pricing, sizes, and color options. Represent the Gyrfalcon project and get a shirt!
A studio for bird study
Tag: raptor
April 11, 2015
Female Barn Owl “Spottiness” Signals Genetic Quality
by Bryce W. Robinson
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
March 31, 2015
Light Morph Harlan’s Hawk – A Noteworthy Specimen
by Bryce W. Robinson
Adult light morph “Harlan’s” Red-tailed Hawk – Buteo jamaicensis harlani
I wanted to share this specimen I found today while going through the small bird collection at Boise State University. It is a great example of the variable traits of the Red-tailed Hawk subspecies harlani. I really enjoy the variable plumages of the Red-tailed Hawk in North America. At the top of my list, as with most Red-tailed Hawk fans, is the Harlan’s.
Here are a few things I found interesting when I first found the bird:
- Some tell-tale light Harlan’s traits – whitish head with streaking, red/pink tail fading to white/gray at the base (Harlan’s tails are ultra variable, but I’ve seen this regularly on light Harlan’s), Harlan’s spotting on tail, warm tones in upper tail and dorsal area, blotchy streaking on belly band.
- Some not so Harlan’s traits – orange barring on leggings (typical of western RTHA), and barred belly band accompanying blotchy streaking. Strange and neat! Also of note is the amount of red in the tail. Common in Harlan’s, but often confused as a sign of intergradation.
I’m a bit disappointed that the tail wasn’t spread at preparation, so it was difficult to get a full glimpse of each feather. Additionally, there was no informative data accompanying the specimen, apart from a tag that read “Red-tailed Hawk”. As I’ve become more familiar with the art of museum preparation and the usefulness of specimens in research, I’ve become more aware of how important information is to put a specimen into context.
Even though the data is lacking, I’m really appreciative of the opportunity to look at this bird and take some photos. It’s a really interesting light morph Harlan’s that deserves some recognition. It made my day.
For some more insight into variability in light morph Harlan’s, check out this article by Jerry Liguori:
http://www.hawkwatch.org/blog/item/810-atypical-harlan-s-traits
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