In the Spring 2012 issue of BirdScope
from the Cornell Lab of Ornithology, an article intrigued me about the song of the House Wren
. It claimed males can sing 600 times an hour. That claim caught my attention. On May 21, 2012
, I made the same claim based on my own backyard observations. I counted songs for several timed intervals that day during lunch on the deck. That is 6,000 in a 10 hour day. That is 180,000 in a month of 30 days, or 1,080,000 wren calls in 6 months. I don't know how it does it. Such a little bird and so much sound. I am glad it can do it. They are one of the most vocal and welcome guests in our backyard. Another is the Gray Catbird
The story goes on to describe an analysis of the frequency spectrum for the House Wren song. (Yes, of course, there is science stuff in this post. Isn't there always?
Quoting the author, Becky Cramer...
Just the mechanics of how a half-ounce bird can make this much sound fascinate me. But as a graduate student at the Cornell Lab of Ornithology, I also wonder why they do it. If a Swamp Sparrow can claim its turf with a simple trill; if an Eastern Phoebe can woo mates with a scratchy "fee-bee," then what is the extravagant fuss of a male House Wren all about? After five years of research I'm still not sure I know-the wrens' songs are just so complex-but I've learned a lot about sound and song in the process.
Click on the image at the right. It should take you to the article. Part way down the article you will find two audio recording controls, the same as pictured in this image. One plays the wren song at regular speed. The other plays it at one quarter speed for comparison. There is an amazing amount of frequency information packed into that song.
How does one extract that information for study?
The author uses the spectrogram
. Time is on the horizontal axis. Frequency of sound is on the vertical axis. It samples a wren song one millisecond at a time. It show points where both sides of the bird's syrinx
, or voicebox, sing different notes simultaneously. It displays the complexity of the ending trills. There, the wren sings precise repeats of several different phrases, all within a couple of seconds. Below is an example of a wren spectrogram from the article.
As you might imagine, some songs are harder to sing than others, and many scientists think birds respond to degree of difficulty in a rival's or potential mate's song. Perhaps it's crucial, even for an expert songster like the House Wren, to push their abilities to the absolute maximum, like jazz musicians trading solos.
The author decided to test the effect of trill performance. She played songs with different performance levels to male House Wrens in the wild expecting males to be less impressed with lower-performance trills and to act more aggressively toward them. She noted the trill performance of males that females chose as mates. Maybe the females would respond more favorably to higher-performance trills. House Wrens didn't seem to notice trill performance at all.
Perhaps these songs are too complex to assess even with this relatively sophisticated measurement. One thing's for sure, there are plenty of other difficult aspects to a House Wren's song. But as we keep at it, I'm confident we'll be better able to wring information out of the songs birds sing. And I'm sure we'll be using spectrograms to do it.
What's going on in your backyard?