A studio for bird study

Tag: drawing

Gyrfalcon (Falco rusticolus) Painting

by Bryce W. Robinson

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Gyrfalcon (Falco rusticolus). 11 x 17″ Gouache on paper.

Over the past three years my study has revolved around the Gyrfalcon, as I’ve pursued my Master’s of Raptor Biology degree at Boise State University. In May I completed my degree and finished my thesis. At the moment, I’m doing field work in Alaska with the U.S. Fish and Wildlife Service on a few different bird projects across the state, but I’m also working on getting my Gyrfalcon work published. As my work gets published (hopefully) I’ll be sure to share links and a brief description of what each paper details.

While in school I did my best to be actively illustrating and painting birdlife. I’ve painted a number of different species over the past three years, but I’m left with the feeling that I did not paint my subject species enough. I suppose this feeling indicates that I’ll need to regularly return to painting the Gyrfalcon. I’d like to illustrate some of the concepts detailed in my research, but for now I decided to paint a simple head shot of the Gyrfalcon as a cessation of my “structured” work on the species. Now the page turns to a new chapter, the subject of which is unknown to me but I get the feeling it may be quite broad.

Singing Bluethroat

by Bryce W. Robinson

Singing Bluethroat

Singing Bluethroat – Luscinia svecica. 11 x 17″ prismacolor on bristol. Image copyright Bryce William Robinson.

On every North American birders “must see” list of Alaskan specialties is the Bluethroat – Luscinia svecica. Not only is this a bird with a restricted North American breeding range, it’s aesthetics and behaviors make it one of the holy grails of an Alaskan bird trip.

I’ve spent a fair amount of time in the habitat that the Bluethroat occupies. I’ve heard many singing males, and on occasion I’ve really listened to them. The Bluethroat sings a compilation song, featuring samples taken from sounds in its surroundings. When I’ve listened and put effort into teasing out each component, I’ve heard the iconic “cricket” chirp which interrupts a mash up of American and Pacific Golden-Plover, Golden-crowned Sparrow, Fox Sparrow, American Tree Sparrow, Gray-cheeked Thrush, Arctic Warbler, and many more. It’s a strange challenge, but a lot of fun. The Bluethroat tends to sing in flight, while doing a flutter like display before descending to a perch. However at times I’ve seen a Bluethroat in an intense song bout, perched atop a willow. It’s these times that I’m able to really watch the Bluethroat, while listening to his repertoire.

It’s no wonder why birders fancy this bird. The male has a multicolored throat that stands out in the brown landscape during their pre-breeding displays. As a mimic, their song fits an old world trend which betrays its natural history. The Bluethroat is an old world species, with a breeding distribution which just leaks into North America. For the birder that goes beyond sight and sound, the distribution adds to the allure.

I don’t get to illustrate much while doing field work here in Alaska. Rarely, poor weather and a break in the work will provide me the opportunity to sit down and draw. I’ve had the Bluethroat on my list for a very long time, so I thought I’d seize the rainy days here in western Alaska. Next I’ll be focusing on more Gyrfalcon illustrations.

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

Tail Pumping Behavior in the Black Phoebe

by Bryce W. Robinson

Black Phoebe - Sayornis nigricans. 14 x 17" prismacolor on bristol board. Image copyright Bryce W. Robinson

Black Phoebe – Sayornis nigricans. 14 x 17″ prismacolor on bristol board. Image copyright Bryce W. Robinson

The Black Phoebe – Sayornis nigricans in it’s simple suit of black and white, catches the eye of anyone remotely keen on the goings on of the natural world. This phoebe demands attention, even in a guild of flashy desert denizens. In doing so it provides some quality behavior birding that never disappoints.  

One behavior I have noted while watching the bird forage is the methodic tail flick, not uncommon in the family Tyrannidae, but somehow unique in the Black Phoebe. I’ve wondered about the habit, but never sought to satisfy the wonder until now. The illustration above came about in preparation for the coming San Diego Bird Festival that I will be attending. In practice, I decided to couple the illustration with looking into any insights in the literature regarding the tail pumping habits of the Black Phoebe.

In little time I found a paper (Avellis 2011). The study addressed four hypotheses explaining the behavior, the Balance Hypothesis where the phoebe tail pumps to maintain balance atop unstable perches, the Foraging Enhancement Hypothesis where tail pumping increases foraging success, the Signal to Territorial Intruders Hypothesis where the tail pumping signals conspecifics of the birds fitness and establishment on a territory, and the Signal to Predators Hypothesis where the tail pumps exhibit the birds vigilance amidst predators.

The results of the study indicated the following:

Balance Hypothesis – Not supported

Foraging Enhancement Hypothesis – Not supported

Signal to Territorial Intruders Hypothesis – Not supported

Signal to Predators Hypothesis – Supported

The paper reports that the Black Phoebe increased tail pumping rates significantly when a predator was detected either visually or audibly. The suggested purpose of tail pumping then is to advertise the birds awareness to the predators presence. Tail pumping communicates the phoebe’s health, and that it in turn will be a more difficult prey to capture.

So, when asked why the Black Phoebe pumps its tail, I’ll answer that the behavior is to exhibit the birds vigilance, acting as a deterrent for predators looking for the path of least resistance for procuring food. Another day, another bit of knowledge gained.

Referenced Literature:

Avellis, G. F. 2011. Tail Pumping by the Black Phoebe. The Wilson Journal of Ornithology 123:766-771