Guest blog post at Biodiverse Perspectives

Check out my guest blog post at BioDiverse Perspectives. The post is part of a biodiversity challenge discussed here

The long and short of it:

Tomorrow, your favorite focal biological unit of research (molecule, gene, organelle, organ, organism, ecosystem, general law of nature) will be deleted from the face of the earth. What are the implications?

I wrote about a world without one of my favorite molecules, norepinephrine (aka noradrenaline). Read the post HERE!

Dissertation Defense!

Whoo! For the past five years I have been studying the influence of the social environment on the behavior and brain of the furtive, feisty Lincoln's sparrow (Melospiza lincolnii). I determined how exposure to songs that were either more or less attractive influenced mate preferences in females and influenced singing behavior in males. I also determined how experience with these songs influenced dopamine and norepinephrine in auditory regions of the brain.

Last week I (successfully) defended my dissertation. If you haven't seen and heard enough about songbird brains and behavior, you can watch the defense right here:

When songs aren't so straightforward

I have delved into measuring different aspects of Licoln’s sparrow songs. I do all of these measurements on a visual representation of sound, called a spectrogram. The spectrogram represents the frequency of sound on the vertical axis and time on the horizontal axis. The intensity of the spectrogram’s color represents its amplitude. 

Bird song represented as a spectrogram. Frequency (pitch) is in kHz, time is in seconds. 
The intensity represents the amplitude of the song (photo credit: Langmore 1998). 

The analysis of Lincoln's sparrow song first involves breaking the songs up into their component parts, which we call syllables, (and trills when the same syllable repeats). I then measure different aspects of the songs, how long are the trills, what are their frequency ranges, how many trills and syllables are in the song.

Example of a Lincoln's sparrow song showing the different parts
(trills are outlined in red, individual syllables in purple).

Like so many things in science, when I first started to do these analyses I thought they were relatively routine, clearly defined measurements. Then, as I encountered more songs, I began to get ambiguous cases. Were the trills really trills or just long, complex syllables? Was the song really a song, or just a complex call? One of the greatest sources of fascination in biology can also be a biologist’s greatest source of frustration. Biology is all about variation, and often the more you try to classify that variation the more likely you are to find someone breaking the rules. 

In my most recent project, I am trying to classify each syllable of a song into a unique syllable type. This is both a fun and frustrating process for Lincoln’s sparrow songs. So far, I’ve been classifying syllables by looking at spectrograms and listening to the songs.

Spectrograms of three different songs from different males. In each song,
most of the syllables are unique, but all of the songs share one syllable type (outlined in red).

I’ve got some pre-established rules to classify syllables. Still, I come across cases where it is difficult to decide whether two syllables are the same type or are different. In these cases, I do what anyone does when they are faced with difficulty and uncertainty: I get a second opinion. For now that second opinion is in the form of a human. In the future though, I hope that second opinion will be in the form of a computer program that can objectively categorize syllable types. That's right, I’m going to ask the machine.

If you’ve made it this far in the post (I’m talking to you, Mom), you may be wondering, who cares about syllable types? Well, I care about them for a couple of reasons. Once I can classify syllable types, I can figure out if males sing different syllable types in different contexts. For example, I can ask if males vary their syllable types based on the presence or absence of a rival. Second, I can figure out how males learn songs. Since juvenile males learn their songs from adults, I can figure out what types of syllables juveniles choose to copy from adults by comparing their spectrograms. 

*Want to learn more about spectrograms? Check out Bird Song Hero

Love Ballads

My fiancee is a man of many skills, and while to this day he continues to woo me with his passion for tree identification, his penchant for gardening, and his unwavering dedication to home-brew, it was his guitar playing that first won my heart. Early in our courtship, Chris did everything right (at least when it came to guitar playing). He played on request, he performed heart-felt love ballads, he meandered through a long list of originals. Our relationship progressed as wonderfully as could be, and I couldn't have been happier. Except as we grew closer, and ultimately more comfortable with each other, something changed when it came to the guitar playing, or any music production for that matter. it got weird...

I think it really started with "Dido's Lament," a song from the opera "Dido and Aeneas." As you may know, this is not a happy song. Well, Chris loved it, he wanted to learn it through and through, he played it all the time...All. The. Time. That would have been bad enough, considering how much of a downer songs about heartbreak induced suicide can be. But worse yet, instead of playing the song through, from start to finish, accompanied by vocals, he would play one chord over and over and over, skip to the end, finish at the beginning. Chris stopped performing when he played, Chris was practicing, Chris was exploring...

I know what you are thinking at this point, you are wondering: Is Chris a male songbird? Well, he's not, but I understand how you could get confused. Male songbirds sing to woo lady songbirds, and since they learn the songs they sing, they need to practice, and to hear themselves sing in order to keep their songs hot. In some species of songbirds, males reserve for females special, more consistently performed songs, called directed songs. Females swoon for these directed songs. However, when males aren't in close contact with and actively courting females, they'll sing another type of song, called undirected song, which is more variable and inconsistent. Some researchers think that undirected song is used for vocal practice and exploration.

Example spectrograms of directed song (top) and undirected song (bottom) in Zebra Finch (from Jarvis et al. 1998)

Given Chris' predilectioned for performance level love ballads early in our relationship, when he was actively trying to win my heart, which only later transformed into noise-art style renditions of Dido's Lament, I see how you could confuse Chris with a male songbird, I know I often do.

How do birds switch from undirected to directed song when put in the presence of a female? Well it seems it has a lot to do with firing patterns and neural activity in parts of the songbird brain that control song. These brain areas are more active during undirected song, their activity is more regulated during directed song.

Scientists still don't completely understand how the songbird brain regulates directed vs. undirected singing, and it is even less clear how the human brain regulates singing. However, there is some evidence that different types of singing activate different regions of the human brain. So, even though Chris is clearly not a male songbird, and even though singing evolved separately in birds and humans, the similarities between the two types of vocal communication are quite interesting, and point to common selection pressures to communicate effectively across a diversity of environments and situations.