The first tiny House Wrens returned last week. Their singing will seem non-stop for the next six months. For their small size, they make a lot of cheerful sound. This one occupies the house attached to our back deck. I wrote about his attempts to fill it with twigs in this recent post.
The Spring 2012 issue of BirdScope from the Cornell Lab of Ornithology had an article about the song of the House Wren. The author claimed males can sing 600 times an hour. I confirmed that claim using my own backyard observations. During lunch on the deck, I counted songs for several timed intervals and got basically the same result. That is 6,000 calls in a 10 hour day, 180,000 in a month of 30 days, or 1,080,000 calls in 6 months. I don’t know how they do it. Such a little bird and so much sound. Wrens are one of the most vocal guests in our backyard, along with the Gray Catbird.
The BirdScope story describes an analysis of the frequency spectrum for the House Wren song.
Quoting 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.
The song of the House Wren article is interesting. Part way down the article on the right side of the page you will find two audio recording controls, the same as linked here. The first one plays the wren song at regular speed.
The second plays it at 1/4 speed for comparison. Notice the amazing amount of frequency information packed into the 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 4 trills where both sides of the bird’s syrinx, or voicebox, vibrates to sing different notes in rapid alternating patterns. It displays the complexity of the ending trills. 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 BirdScope 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. – B. Cramer
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. – B. Cramer