Ornithologi

A studio for bird study

Tag: science

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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High Numbers of Swamp Sparrow documented at Ted Trueblood WMA, Southwest Idaho

by Bryce W. Robinson

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My friends Jay Carlisle, Heidi Ware Carlisle, and I had a Melospiza morning at Ted Trueblood WMA, helping Boise State grad student Kate Owens and her fiance Ben trap Song Sparrows for Kate’s Master’s work. The highlight was catching 27 Melospiza sparrows at once, including 10 Swamp Sparrows (M. georgiana), 5 Lincoln’s Sparrows (M. Lincolnii), and 12 Song Sparrows (M. melodia). The incredible number of Swamp Sparrows left us reeling, since we had visited the area twice already this fall for Southwestern Idaho Birder’s Association and Golden Eagle Audubon Society field trips. Our first visit yielded no Swamp Sparrows, and a week ago we detected only 4 individuals (a high count for the site at the time). While processing our 10 Swamps, two remained in the reeds nearby calling, providing us a total of 12 Swamp Sparrow’s for the site! All Swamp Sparrows were young of the year, likely indicative of a productive breeding season for the species. Also notable, all birds had good fat and muscle scores which is indicative of good health, and upon release flew away with vigor.

Ted Trueblood WMA has been very generous to us in the past, hosting two of the three Idaho state records for Le Conte’s Sparrow. It continues to be a state sparrow mecca with this incredible high number for Swamp Sparrow, and who knows what will turn up in the future.

I’ve included here some photos of our morning, including a photo of four Swamp Sparrows at once, and a photo of all three members of Melospiza aside a painting I illustrated of the genus (by the way these prints are available in the shop). You can also see our numbers for the site and other species we documented, including a conservative estimate of American Tree Sparrow (Spizelloides arborea) on our eBird list:

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Photo: Heidi Ware Carlisle

 

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Just Published in Marine Ornithology: Unusual Foraging Observations Associated with Seabird Die-offs in Alaska

by Bryce W. Robinson

 

Above is a short video that I produced to supplement a paper I, along with colleagues at US Fish and Wildlife Service and USGS, just published in the journal Marine Ornithology. The video shows behaviors that we describe in the paper, and will hopefully help the reader visualize what we experienced ourselves.

The Bering Sea region is changing in many ways, but among the most sobering are the mass die-off events that are impacting the regions birdlife. These die-offs continue into this year. Since we put together this publication of the observations that I and colleagues made in 2016 and 2017, the trend has continued and is likely to continue into the future. Furthermore, on my most recent trip to the region I documented further evidence of the ongoing change that is occurring across the bering sea ecosystem. There is and will continue to be more to report.

Some of the change, such as the evidence of starving and ill affected storm-petrels that are the subject of our publication, is sobering and concerning. It hits hard on the hearts of those of us who so passionately pay attention to bird life across the globe. We care deeply about the well being of these creatures that fascinate us so much.

Some of the change, such as some of my most recent observations in the region, are exciting and stoke curiosity, as the birdlife of the region responds to the impacts of ecosystem disruption.

Ultimately, there will be winners and losers as life navigates anthropogenic driven change throughout the world. Mass die-off events will become the norm for some species, until their populations can no longer sustain such losses and they are eventually lost to our world. Others will adapt in ways we cannot yet imagine. Such adaptations will undoubtedly open our minds to processes and function in ecosystems that we are yet to understand.

Yes, climate change is a problem. It is a problem that still is not unanimously recognized. It will change our world, our way of life, and probably not for the better. But, as we experience the change, we can document what is happening for the future inhabitants of our perturbed ecosystems. We can make record of the oddities, the aberrations, so that we leave a paper trail of first observations that will help us understand when things started, and how they developed. Hopefully, as these records build the evidence of change will become insurmountable to the point that the overwhelming majority of our society cannot and will not deny that the world is impacted by our daily choices and we ourselves need to change. And when we do, hopefully it will not be too late.

This is why I want to publish notes such as this, to make a record that will add to the evidence of an increasingly disrupted world. More to come…

You can find the paper detailing our observations of odd foraging behaviors here:

http://www.marineornithology.org/PDF/46_2/46_2_149-153.pdf