Some people can trace their traditions back decades; the swamp sparrow has passed its songs down for more than 1500 years. The findings, published today in Nature Communications, suggest humans are not alone in keeping practices alive for long periods of time.
To conduct the study, researchers recorded a collection of songs from 615 adult male swamp sparrows from six densely populated areas across the northeastern United States. They dissected each bird’s song repertoire, identifying only 160 different syllable types within all the recorded sample. Most swamp swallows sang the same tunes, using the same common syllables, but there were a few rare types in each population, just as there are variations in human oral histories over time.
Using a statistical method of calculation called approximate Bayesian computation and models that measure the diversity of syllable types present in each population, the scientists were able to calculate how the songs of each male would have changed over time. They also found that all but two of the most common syllables used during their sampling in 2009 were also the most common during an earlier study of the species when recordings were made in the 1970s. Overall, the analysis indicated that the average age of the oldest tune dated back about 1537 years.
Other bird and animal species may also be capable of similar feats, the researchers say. Even animals with relatively small brains can have long-lasting traditions.