The Dictionary of American Regional English closed its doors this year, more than five decades and six volumes after the zealous undertaking began. Documenting words, phrases, and pronunciations that vary across the United States, the Dictionary retains those roots and customs with a unique heritage. Researchers with DARE have documented complex linguistic evolution and severing through time.
Studying thousands of cities in the US, the team discovered and mapped incredibly localized phenomena. However, they didn't study sparrows. They studied sparrowgrass—or asparagus—in some areas, but they failed to study sparrow language.
As it turns out, white-crowned sparrows have their own dialects, their own dictionary of regional sparrow, if you will. In the 1960's, researchers in the San Francisco Bay Area discovered differences in the songs of white-crowned sparrows. Based on neighborhood, the sparrows had markedly different songs, and held a fidelity to those areas with their dialect. Young white-crowned sparrows do not learn directly from parents but rather from the general acoustic environment where they are raised, the researchers later proved. Thus, because the sparrows learn from their surroundings and because they have a restricted geographic range within the city, dialects form.
The content of the white-crowned sparrow's song carries with it other messages beyond the varying spectograms (pictures of sound) of the San Francisco Bay Area. In Colorado, researchers found that white crowned males that are infected with blood parasites will have different songs with fewer trill notes than uninfected males. These parasites can reduce brood success by 15-20%, and thus females can determine which mates will be successful based on the fitness of their song.
Back in San Francisco, researchers have followed up studies from the 1960's with current data on song dialects in white-crowned sparrows, with surprising results. One of the dialects has vanished. Even more surprising was the likely reason: traffic. The San Francisco dialect, with its highest minimum frequency, was able to out-compete other dialects. Those birds with the San Fran dialect were singing their high pitched song over the bustle of a growing city with ever-increasing traffic loads, and successfully attracting a mate because of it.
Yet, this adaptation may come at a cost. Females seem to prefer the low pitch song, but that's a dialect fast becoming threatened and already hard to hear. This research into sparrow language has proven a complexity of adaptation and choice for females. The extinction and malleability of song also suggests a possible rapid evolutionary pathway—beyond song, those California city birds average smaller territories and blacker wings. The territories are thought to be collapsing because males cannot hear their aggressive competition over the noise of the city. It's also possible that the darker wings help concentrate metals and toxins outside of the body.
These white-crowned sparrows are some of the most studied birds in terms of song and the evolution of song. What breakthroughs could be achieved studying the other 913 birds species of North America? How many volumes would the dictionary of regional bird have?
Here at Faville Grove, it's hard to miss the white-crowned sparrows. Down Prairie Lane or North Shore Road, you'll see flocks of the birds flitting through the prairies as they're on their way south for the winter. Some will overwinter. The white-crowned sparrows don't breed in Wisconsin, instead preferring the high arctic in summer, but their white crowns en masse bookend the winter each year.
Written by Drew Harry, Faville Grove Sanctuary land steward
Banner photo by Kelly Colgan Azar