Ornithologi

A studio for bird study

Tag: tundra

Differentiating Adult and Juvenile Gyrfalcon (Falco rusticolus)

by Bryce W. Robinson

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Given that much of my career has been focused on the world’s largest falcon, the Gyrfalcon, I often get questions about their life history and Identification. A recurring question is the age of individuals that are observed in winter. Most often, folks ask about juvenile vs. adult, so I decided to make available a simple illustration with annotations as a reference for those with these questions.

What I’ve realized is that fleshy parts confuse a lot of people, since an adult should have yellow legs and cere, whereas a juvenile should have blue. However, it takes female birds much longer to change (well into their second year), and the coloration is also influenced by individual quality and hormones. Some adults, particularly females, tend to be quite dull in the winter (compare this with observations of gull legs in winter, e.g. California Gull). Adults that are likely three years or older (given presence of retained feathers in the upper wing, etc.) can have surprisingly dull legs that may appear blue under certain conditions. The key then is to take a step back and focus on the plumage, since in most cases it is quite straight forward.

The illustration above aims to highlight the key points for aging a Gyrfalcon between adult and juvenile. Eventually I’d like to visually describe more micro-aging factors, but for now I think this will be a helpful resource for those more unfamiliar with this species.

Please, feel free to send me feedback and suggestions. Constructive criticism is always welcome.

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Gyrfalcon (Falco rusticolus) Plate

by Bryce W. Robinson

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My friend Kenneth, a Gyrfalcon researcher in Norway, is perhaps the most enthusiastically obsessed Gyrfalcon lover I know. I really appreciate his passion for the bird. Next week he is traveling to Salt Lake City for the Raptor Research Foundation’s annual conference. He asked me to paint a Gyrfalcon portrait for him, so I decided to take the opportunity to illustrate some perched birds to populate the plate I’ve been putting together. I going to produce some giclee prints of this plate, but I’m limiting it to 20 prints. If you like this image, and would like to purchase a print, it is available in the shop!

It’s taken me some time to paint birds that I’m pleased with enough to put into plate form. I’m still a bit at odds with these birds, but I think the above image best fits what I’m going for in creating the plate. My next step will be to paint some different postures and explore which best fills the gap in understanding the different positions and appearances that a Gyrfalcon may take on, in varying conditions. Additionally, the plate needs multiple different in flight postures, and some other age and plumage morph descriptions. Progress has been made either way, and I’m excited!

Below is the painting that I did for Kenneth, as it will look to him. I’ll be traveling to Salt Lake City myself, with this painting alongside me. Thanks for the opportunity Kenneth!

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Just Published: Applied Raptor Ecology: Essentials from Gyrfalcon Research

by Bryce W. Robinson

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The Peregrine Fund just released a new book, “Applied Raptor Ecology: Essentials from Gyrfalcon Research”. This book serves as a techniques manual geared towards providing early career researchers with information and a stepwise guide for conducting various research on raptors. This information is also supplemented by mock data, and R code to help the researcher begin to form skills in R and analysis.

Although I am the clown in orange on the cover, my true contribution is found inside the book. I contributed as an author of a chapter – Quantifying Diet; an appendix – Guidelines for Conducting a Camera Study of Nesting Raptors; and as coauthor of an appendix – A Photographic and Morphometric Guide to Aging Gyrfalcon Nestlings.

For more information and to purchase the book, go here:

http://science.peregrinefund.org/applied-raptor-ecology

*PDF’s of each chapter will be available January 2018

Published in the Wilson Journal of Ornithology: First record in birds of nestling relocation following nest collapse

by Bryce W. Robinson

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Photo of a female Gyrfalcon holding a surviving nestling following partial collapse of the nest. Photo published in Robinson, B. W., N. Paprocki, D. A. Anderson, and M. J. Bechard. 2017. First record of nestling relocation by adult birds following nest collapse. Wilson Journal of Ornithology 129 (1) 216-221 

Since I’ve been hard at work in central America for the past month, I haven’t had the time to share a recently published article from my Gyrfalcon work. The article details the behavioral response of a female Gyrfalcon following the partial collapse of a nest. The photo above shows her holding the only surviving nestling following the partial collapse of their nest on a cliff side in Alaska. Just moments later, the female took the nestling to safety at another ledge farther down the cliffside. This behavioral response to threat is the first documented case in altricial birds!

Read the full article: 

Robinson, B. W., N. Paprocki, D. A. Anderson, and M. J. Bechard. 2017. First record of nestling relocation by adult birds following nest collapse. Wilson Journal of Ornithology 129 (1) 216-221