A studio for bird study

Tag: raptors

Notes on Gyrfalcon Molt

by Bryce W. Robinson

Adult Male Gyrfalcon - Falco rusticolus

Photo 1. Adult Male Gyrfalcon – Falco rusticolus

I like to pay attention to molt in birds. There are many aspects of a birds life history that can be reflected by their strategy for feather replacement. A great example is something I’ve been watching with the nesting Gyrfalcons I’ve been working with lately.

Last summer, I noticed something about the molt between male and female Gyrfalcons. While I was entering nests to install cameras in the early nesting period (mostly during incubation), I noticed that males were behind females in their molt progression. Following my initial observation, I started paying closer attention to each bird. I continue to take notes on this, and wanted to share the molt of a pair from a nest I visited recently.

Adult Female Gyrfalcon - Falco rusticolus

Photo 2. Adult Female Gyrfalcon – Falco rusticolus

You can see that the male (photo 1) has just dropped his fifth primary. Falcons generally begin their primary molt at P 4&5 and progress in two directions. The female (photo 2) has dropped her third, fourth, fifth, and sixth primaries. You can see P 4&5 are growing in already.

This illustrates a few simple things in the life of a Gyrfalcon. One, that energetics govern the ability to molt. Two, that male and female Gyrfalcons have different energetic roles and energy budgets during incubation and early brood rearing. They have different roles in the process. These are illustrated by the fact that they differ in the progression of their molt.

Later, the rates even out as both adults need to provision for their growing brood. I hope to get photos of this pair on my next visit to the nest in a few weeks.

Peculiar Plumage of the Harlan’s Hawk

by Bryce W. Robinson


I found this interesting Harlan’s Hawk today in Hagerman, Idaho. It’s overall plumage left me thinking about Harlan’s ID. I’ve heard many people describe the “distinguishing” characteristics of the Harlan’s Hawk, but I’m always left confused as most of the Harlan’s I’ve seen don’t quite fit the mold they describe. I only know of a handful of people that can properly articulate why a bird is a Harlan’s, or not. In fact, I don’t include myself in that small list. I can recognize the subspecies, but putting that recognition into words is challenging. I believe this is due to the extreme variation in these hawks.


The white lores and flecking against a dark background on this bird are the only part of the body plumage that tips the filter for Harlan’s. It is not the deep black that everyone describes for the subspecies, nor is it highly contrasting. To be clear, this bird is very dark, but I’ve seen many Calurus that are highly melanistic, with deep dark brown bodies, even with light markings on the breast not unlike this bird. Many of the Harlan’s in Alaska and the Yukon Territory that I saw this past summer were soft brown, not at all high contrasting in plumage. This variability causes some confusion. So what makes a Harlan’s? As with all bird Identification, the ability to recognize a bird comes with study, exposure, and the overall impression of the bird. I have always compared bird identification to facial recognition, where multiple factors contribute to a recognizable image, without any cognizant processing. I leave the breakdown of what specific factors contribute to Harlan’s identification to the true experts, like J. Liguori.


At times, there are single clinching factors that seal the deal in bird ID. For the Harlan’s, it is the iconic tail, the one mysterious trait that causes we the birder so much awe and admiration. But, I’ve seen Harlan’s with red, banded tails. Most of the birds I saw in the north last summer had extensive red in the tail. The Harlan’s tail can often be misleading. This fact, coupled with the variation in body plumage leads to the point of considering every bird as a whole.

The bizarre tail of this bird is fascinating. The central feathers are half ghostly silver, and half solid dark. The others are irregularly banded and spotted against a background of soft reddish tones reminiscent of its specific designation. After encountering this bird, I’m left with one question: Are any two Harlan’s alike?

Prairie Falcon- Falco mexicanus

by Bryce W. Robinson

Prairie Falcon- Falco mexicanus. 18x24" prismacolor on bristol

Prairie Falcon- Falco mexicanus. 18×24″ prismacolor on bristol

Of all the raptors I illustrate, it seems falcons give me the most trouble. I’m not entirely sure why, but the fact that I struggle with the family is a bit disheartening, as it is likely to be a group I spend a considerable amount of time studying for the rest of my life. Perhaps with time, I’ll work out the bugs in my inability to adequately illustrate the birds.

Falco mexicanus is a significant illustration for me. I’ve conducted a great deal of field work in the west, primarily in the flats of the great basin, and I’ve had many experiences with the sandy brown assassin. Get yourself lost on lonely dirt roads of the remote great basin in midst of winter, and you will undoubtedly come upon a Prairie Falcon perched on some high point, surveying for prey.

I remember last year, I was searching for eagles on the edge of the salt flats of north western Utah. I had pulled over to glass a mountain top, and found myself watching a perched Golden Eagle, some two kilometers away by my estimate. While I watched the bird, I notice a fast approaching figure headed straight for the large raptor. The figure was in fact the Prairie Falcon, come to conduct its business of bullying the large eagle. The tenacious bastard kept at it for nearly five minutes, until finally the eagle had enough of the dodging, and fled from the persistent falcon pest.

My success with illustrating this bird is fortunate, and gives me the courage to start a project that will be focused on gleaning some much needed extra funding for my work with the worlds largest falcon this summer. Stay tuned as this idea develops and materializes.

Maintaining a Creative Outlet is Necessary for Study

by Bryce W. Robinson


Ferruginous Hawk- Buteo regalis. 8×11″ Prismacolor on bristol

I’m currently in the midst of my first semester of graduate school. I’m pursuing a degree in raptor biology, which entails loads of technical study and analytical understanding. While I’ve saturated myself with technical thinking, I often feel the urge to exercise creativity. This urge has come to conflict with my current aspirations and responsibilities, but after some reflection, I’ve settled on a solution to this conflict by accepting the urges and managing my time in a way that allows me to embrace and express my creativity. I really believe that in the end, maintaining a creative outlet will ultimately strengthen my study of raptors, and strengthen my critical thinking.


Rough-legged Hawk- Buteo lagopus. 8×11″ prismacolor on bristol.

I’ve featured two Illustrations that I’ve done since I started classes. I am going to continue with the raptor illustrations, but I’ve decided to start focusing on painting again as well. If anyone has a request of something they would like to see me illustrate or paint, feel free to let me know. I always appreciate a little direction.