Linked paper: Four decades of cultural evolution in House Finch songs by C. Ju, F.C. Geller, P.C. Mundinger, and D.C. Lahti, The Auk: Ornithological Advances 136:1, January 2019.
The first bird song I ever recorded was that of a House Finch. When I was a kid growing up in Leominster, Massachusetts, the bird that nested behind my front porch lamp would fly out to a particular birch tree or the telephone wire and belt out a complex four-second warble over and over again. That sound became emblematic of summertime for me and my siblings. One day when I was in my room holding my tape recorder against the radio speaker to record songs (human songs, that is!), I heard the little red fellow outside start doing his thing, and I promptly stuck my recorder out the window for an acoustic memento. I actually ran across this cassette tape for the first time in nearly four decades a couple of months ago, coincidentally just as my first scientific paper on House Finch song was about to be accepted for publication in The Auk.
Here are a couple of examples of House Finch song. Read it like sheet music, with time on the horizontal axis and pitch on the vertical—it’s composed of a bunch of notes, or syllables.
The reason my research collaborators and I are interested in House Finch songs today is because these songs change over time and space—we’d like to know how and why they change the way they do. Most animals simply inherit the noises they make, and so the sounds don’t change much from generation to generation. About half of the world’s birds, however, learn how to “speak” as juveniles from older members of their own species, just as we humans do.
The youngsters don’t always imitate perfectly the songs they learn, and so over the generations small changes in these songs can accumulate. These changes result in noticeable song differences across time and space, just as we humans diverge in our accents and languages. For this reason, bird song is an important animal model system for the study of cumulative change in socially learned traits, what’s known as “cultural evolution.”
Long-term changes in bird song are rarely studied, because research projects don’t often last for decades. However, even as I was listening to that House Finch from my bedroom, Dr. Paul Mundinger, a professor at Queens College at the City University of New York, was recording them on western Long Island, in high quality and accompanied by meticulous field notes. Paul had just published a paper in The Condor showing that House Finches can have different song dialects. He had also indicated that young House Finches learn their songs by listening to a bunch of singing neighbors and assembling chunks of syllables from several of them, like an acoustic collage. The end result is two to four songs that an individual will sing consistently for the rest of its life.
Fast forward 37 years, and I, a new professor at the same college, became Paul’s friend and colleague. He was pleased to hear that I wished to pick up where he had left off with House Finch song in the 1970s (after which he had moved on to research on the canary). I was excited to compare his early House Finch recordings to the songs sung by local birds today. Because birds’ generations are so much shorter than those of humans, this would be like comparing our English to that used a millennium ago in the epic story Beowulf, which is so different from our modern language that it would be unintelligible to most English speakers today.
The main two steps in this study would be (1) to see what songs these Long Island House Finches are singing today, and (2) to find a reliable way to compare songs across time. Two doctoral students in my lab stepped up to the task. Franny Geller loves observing and recording birds, and so she recorded as many House Finches as she could find in western Long Island in 2012, and Chenghui Ju is a computational wiz who programmed software specifically to characterize and compare House Finch songs in different times and places. This study became part of Chenghui’s recent doctoral dissertation.
What did we learn? Find out in Part 2!