Home & Garden Columns
It may be a drab little brown bird, but the song sparrow has attracted a lot of scholarly attention. The song sparrows of San Francisco Bay alone support a kind of cottage industry. We have four distinct subspecies here, three confined to tidal marshes, the fourth to neighboring uplands. The marsh sparrows, generally smaller and grayer than the upland birds, have adapted to their environment by evolving a higher tolerance for salt water (although their insect prey appears to meet most of their water needs).
The foundational song sparrow studies were done by Margaret Morse Nice. After her academic career was derailed by marriage and motherhood, she spent most of the Great Depression tracking the lives and fortunes of a song sparrow population along the Olentangy River in Columbus, Ohio. She also found time to collaborate with Konrad Lorenz. According to another pioneering behaviorist, Niko Tinbergen, this “American housewife was the greatest scholar of them all.”
Along with every other aspect of sparrow behavior, Nice paid close attention to their songs. It became clear that there was no such thing as a stereotyped song sparrow song. “The songs of each male are entirely distinct,” she wrote; “as a rule they sound pleasant and ‘cheerful’ to human ears, yet a few are disagreeable, while still others are of great beauty.” Each adult male, she found, had his own repertoire of six to nine song types. And song patterns changed as a bird matured, with a period of improvisation before the repertoire crystallized.
She was curious as to whether songs were inherited or learned, or a mixture of both. After listening to several generations of sparrows, Nice concluded: “I found no case of a male having the song of his father or grandfather on either side.” On the other hand, she heard young territory-holding males imitating their neighbors and sometimes incorporating those songs into their budding repertoires.
She also experimented with captive-reared birds, exposing them to recordings of species they would never have heard in the wild—nightingales, European song thrushes—and noting the odd-sounding songs they developed.
So what was going on? As research expanded to other species, it became clear that many of the true songbirds—the oscine passerines, to be technical—learn most if not all of their vocal repertoire. That’s also true of a few other groups, notably hummingbirds (or the few hummingbirds that can be said to sing).
The process seems to require exposure to a model or “tutor” at the right developmental phase. But were the tutors parents or neighbors?
The evidence on that score is mixed. Male song sparrows reared by canaries copied their foster fathers in one study but not in another.
Luis Baptista, the late curator of birds at the California Academy of Sciences, found a couple of song sparrows in the wild that had somehow acquired the songs of white-crowned sparrows. Juvenile males in Washington state appeared to have learned their songs from holders of neighboring territories. But in a sparsely populated British Columbia habitat, young males retained their fathers’ songs.
Experimental research by John Burt and Adrian O’Loghlen at the University of Washington suggests young birds acquire their songs by eavesdropping on neighbors. From the age of 15 days, fledglings were housed with a rotation of singing adult males. That exposure ended after a month and a half. At eight months, each young bird was paired up with an adult tutor. The youngster was then moved to a separate chamber where he could hear a second tutor interacting with another young bird.
The young males’ songs were analyzed when they were about a year old. Fifty-one percent of their repertoires came from the tutor next door they had overheard. Another 19 percent came from tutors with which they had shared a cage, and the remaining 30 percent from the adult birds they had heard as infants.
Getting your songs right is crucial to attracting a mate. One study showed a female preference for the local song dialect. Repertoire size may also influence mate choice, according to a lab study, although field work did not confirm this. (In any case, song sparrows are pikers compared with western marsh wrens, which may have up to 210 distinct song types.)
As far as I know, no one has studied song acquisition among the Bay’s salt-marsh song sparrows, which occupy small territories year-round in tightly packed habitats. The lucky yearlings that could shoehorn themselves in would be surrounded by potential song models. A likely project for some contemporary Margaret Nice. Bring your waders.
Photograph by Ron Sullivan. A song sparrow at home in the marshes of San Pablo Bay.