Friday, November 18, 2016

Caracara research moving to Arizona!

Hello everyone,

Most of you know I've been studying crested caracaras in Florida for the past 20 years or so.  Now that I am retired from the day to day challenges of academia, I am eager to branch out and investigate other populations of this intriguing raptor, particularly in Arizona.  I am excited about this new research direction because I suspect the biology and ecology of Arizona’s caracaras are very different from what we know about the Florida population.

Starting this winter, I hope to capture and tag with GPS/GSM transmitters, several individual caracaras from the large groups that we have been seeing wintering in agricultural fields, in Arizona.  The goal is to determine where these caracaras feed and roost during winter, then to track them through the annual cycle.  As the human population and urban development continues to expand in Arizona, understanding the biology and status of this caracara population and how individuals respond to land use change becomes ever more interesting and important.

To start this project and get preliminary data, I need $5000 to purchase the GPS/GSM transmitters and to purchase fuel for field vehicles and supplies, as needed, for trapping.  Funds will also be used to develop an interactive website, through which visitors can follow movements of individual caracaras and learn about this raptor’s biology and behavior.

I have launched a crowdfunding campaign on Experiment.com to raise support for my research: https://experiment.com/projects/where-do-all-the-caracaras-that-winter-in-central-arizona-go-during-summer . Once I start capturing caracaras and tracking their movements, I’ll be sharing what we find on my project page and on our website.

I'm reaching out to ask for your support.  If you can’t donate directly, could you please take a moment to share my project?  Even just a social media post, or emailing the project to any friends, family, or colleagues interested in raptors will help make this project a reality.

If you have any additional questions about the research, or how this campaign works, I’ll be happy to answer them.  Thanks for supporting this project, it won’t be possible without you!


Thanks!

--joan

Wednesday, November 16, 2016

Avian Countercurrent Heat Exchange


Birds have it hard up here in the northeastern part of the United States. Strong winter winds, below freezing temperatures, snow covered landscapes and a lack of food makes one wonder “how on earth do birds survive?”

To begin with, resident species prepare themselves for the approaching winter by storing extra energy in the form of body fat, while at the same time, thickening their plumage by growing additional down feathers. This results in a doubling of a bird’s total body mass and an increase in body feather count by nearly 50 percent.

Some species, like the Blue Jay and Black-capped Chickadee, will also collect and store food during the fall, hiding it away for later use during the winter months.

Another interesting behavior finds the American Crow roosting by the thousands in many of our major cities. Experts believe that in addition to providing the crows protection from predators, urban roosts are about 5-10 degrees warmer than the surrounding areas. 

Still others form winter flocks for the sole purpose of conserving each other’s own body heat. I often find gulls and geese huddled together in tightly packed groups, sleeping in safety upon ice-covered coves. Despite this simple behavioral trick, I couldn’t get past the idea that these birds were still losing precious heat through their exposed legs and feet. So how do gulls and geese mitigate heat loss from their bare extremities, and how about frostbite?

In a new book that I have just finished reading called “Beaks, Bones & Bird Songs, How the struggle for survival has shaped birds and their behavior”, Roger J. Lederer nicely explains the process in which birds physically pull this off;

 
Beaks, Bones & Bird Songs
Roger J. Lederer


Source: http://ecology.botany.ufl.edu/ecologyf02/homeostasis.html
Birds have a countercurrent heat exchange system between the arteries and veins of their legs. Blood in the arteries from the heart is warmer than venous blood returning from the extremities. The arteries and veins are intertwined in a structure in the lower leg called the “rete tibiotarsale” (net of the tibiotarsus) which may consist of as few as three arteries and five to seven veins, as in owls, or up to sixty arteries and forty veins as in flamingos. Birds without this net have two veins, one of which runs closely on either side of an artery. The warmer arteries pass on some of their heat to the colder veins, returning some warmth to the heart but still providing enough heat to the legs and feet to keep them from being frostbitten. In some species of gulls and guillemots, the arteries and veins are closer to each other in the birds of more northern areas than those of more southerly locations.

He goes on to write;

Countercurrent heat exchange operates very efficiently. A duck standing on ice will lose body heat, but only five percent of that loss will come from its feet. Of course, blood has to supply oxygen and nutrients to the feet and legs, but only a small amount of blood is needed because the muscles that operate the feet and legs are mainly concentrated in the upper leg and utilize long tendons for mobility. At lower temperatures that threaten the feet with frostbite, blood flow is increased to the lower limbs by opening special valves in the arteries (end).


A gull and its bare extremities
Photo Credit: Paul Cianfaglione 
To fully appreciate their solutions to life’s challenges, we sometimes need to look beyond the field mark and toward the inner workings. Once again, birds reveal another striking structural specialization that has enabled them to invade most of the world’s environments.