Feather Growth and Condition

The mechanisms behind feather growth are very counter-intuitive. Feathers begin to grow at the tip of the feather, the part which, in House Finches, is pigmented. The barbs grow in shafts and collect at their base to form the rachis. This development occurs "in pin" in the bird's dermis. The feather then rolls out and spreads, creating the shape that we recognize.

Because we know the way in which feathers develop, we are able to track the rate of growth of a feather months after the bird's molt. For my project, I take a look into the past and use trigonometry and feather landmarks to find what that feathers rate of growth was during the bird's molt.

I'm going to compare this rate of feather growth to the bird's condition (based upon the mass taken at time of capture). Will birds in worse conditions grow feathers more quickly (hastily) or will they take longer to find the energy to grow the feathers? The most interesting part of this question I will be investigating is the different results between sexes.

Males put much more energy into their feathers, especially House Finches. They must expend extra energy to not only put carotenoids into their feathers but also to modify the carotenoids in their diet to determine their hue and reflectance. I predict that there will be a larger deviation of feather growth vs. condition in males when compared to females because males spend more energy growing their feathers.

I look forward putting out some significant data soon!

Thanks for reading,
Caitlin

When Sexual Dichromatism isn't so Binary

In birds, males are colorful and females are not, right?

Not always. 

Some females find themselves with pigments in their feathers that weren't really meant to be there. What comes from this is irregular feather structure due to different growth patterns, different barb size, etc. There is a variety of reasons why this may happen, the most probable of which being that the female has a hormonal imbalance. Most of the time these anomalies are just a bit of brown on the tip of the rump feathers. However, more rare are the females that develop male signaling colors such as reds and the variant yellow.

The way in which these females' feathers develop suggests a stress response; males with the same pigments' feathers are generally symmetrical and "prepared" for these kinds of pigments. What is different in feather development between females and males such that males are prepared for these pigments while females are not? I hope to answer this and related questions in the coming months. 

Feather Masses

"Light as a feather".

 At this point, I know that phrase all too well. This past week, I was trained in a new procedure which allows us to find the portion of each feather which is pigmented. First, we weigh the whole feather. Then we weigh the pigmented section. Sounds easy enough, right? I thought so at first.

Our study is concerning the pigmentation of house finch feathers. This is what a house finch looks like:

For some perspective on their size, this is someone holding a house finch and one of their feathers:

So you see, it's not all too difficult. In the lab, all we have to do is use tiny forceps and tiny scissors to cut the red tips of the feathers from the rest of them. I have become remarkably good at holding my breath. As my adviser said when he saw me working on this process: "Don't sneeze". I've made the mistake of breathing too hard; I was crawling on the ground for hours searching for crown feathers which couldn't have been more than a few millimeters long.

As I start this task which already has taught me so much patience, I'm also given the opportunity to see how my work is helping. The post-doc that all my work has been helping the past few weeks is presenting her findings tomorrow. I love being able to contribute; I would gladly hold my breath to help anyone I've met in my lab.

Thanks for reading, guys.

Caitlin

Lab meetings

The past two days I have had the privilege to sit in on my lab's meetings. The first was a journal club in which each person scanned through a journal, chose articles which they thought might interest the others, and discussed them with the group. I read some fascinating studies- some of which I didn't totally understand. The most interesting paper which we discussed was concerning the role of double-stranded RNA in transgenerational adaptations, a study detailing the mechanisms of epigenetic a. Although I had to spend a few hours on Google just for the vocabulary, I got through it and was amazed by the end. 

In the second lab meeting, a prospective post-doctoral scientist presented his past, present, and possible future research to our lab. He had been all over the world from what I understood! Much of his study was conducted on European blackbirds in Germany and light pollution's affect on their lifestyles and circadian rhythms. He applied some of his hypotheses to the relationship between light pollution and nature as a whole and related it to recent studies which say that humans may be becoming more obese due to disruptions in their natural circadian rhythms. I had never before considered the affects that light pollution could have on me personally, considering I am not usually aware of it. The discussion afterward was energetic and interesting as well. People were suggesting solutions to certain ambiguities as well as challenging his methods, I find myself wanting to contribute at times. It was a welcoming yet challenging environment which wasn't afraid of intellectual confrontation. What a great feeling!

New feather processes

This last week has been pretty exciting! at the the lab they have been training me to take over some of the bigger parts of the experiment. First I selected one feather from each ornamentation for each bird based on their variation and viability in our programs. After 100 individual house finches and 300 feathers in total, we're moving on to the next step. Last week and this week is going to be a lot of landmarking. 

We use a program to landmark specific points on the house finch feathers so that not only can we compare the presence of pigment between ornamentations, we can also compare the feathers' pigmentation between species. Our program matches up the landmarks that we have marked so we could compare the feather of a house finch with, say, the feather of a flamingo. Their feathers are radically different sizes which is why this program is so amazing and useful.

Throughout the past week I have also been scanning feathers for later analysis. I gather all the feathers that have been collected from individual house finches during field outings, take down all of their data, then prepare them for scanning. After strapping on some gloves and washing everything and the kitchen sink with isopropyl, I use forceps to delicately line up and organize the feathers by ornamentation on the scanner. Then I cover them with a plastic sheet and flip down the cover to scan. This whole process is more difficult than you'd thjnk. The steps themselves are easy to comprehend and describe,  however, the patience required is immense. When placing the feathers (many of which couldn't be a few millimeters long) on the scanning bed, you cannot breathe too hard, you can not make sudden movers. The most frustrating part is the static. As you are placing the plastic covering over the feathers, they will often fly up and stick to the plastic, and you have to start over again. 

Even with all the tedious annoyances, I actually really enjoy it. I don't know that I've always been the most patient person, but this task has certainly made me more patient. It's a challenge and one that I find myself growing better at everyday. I have been learning so much, I think the best part is the accomplishment and sense of contribution I have. I am so grateful that I am able to contribute to a community filled with people that I respect and have been growing closer with for the past few weeks. 

Thanks for reading!

First Week

I couldn't be more excited to start working tomorrow. I will be performing digital image analysis on and finding the carotenoids concentration of house finch feathers in order to compare the ways in which different individuals intake and modify carotenoids.

Birds cannot make carotenoids, a pigment; they can only obtain them through consumption. Then individual birds modify them by, for instance, adding an oxygen to use them how they like. In our lab, we are comparing the presence of various carotenoids within the House Finch species.

Later in the study, we will landmark and compare the carotenoid content interspecially.

This study will give us an idea of how the use of various carotenoids affects the feather structure, how their diet may affect their pigmentation, and why the use of this pigment has been sexually selected.

I feel so lucky to be a part of something so fascinating. I can't wait!