Question

How does Marler’s work on song development in white-crowned sparrows indicate that behavior is shaped by learning? How does it indicate that behavior is shaped by instinct?

Answer 1

In the 1960s, Peter Marler studied song dialects in white-crowned sparrows (Zonotrichia sp.) and found that different populations of the bird have distinctively different dialects.

Marlar et al. (1964) took eggs from the nests of white-crowned sparrows and hatched them in the laboratory where the baby birds were hand-reared. Even when these birds were kept isolated from sounds made by other birds, they started singing when they were around 150 days. However, their song was a twittering vocalization that did not take on the character of the full song of a white-crowned sparrow. This experiment showed that behaviour can be shaped by instinct.

When 10 to 50-day old white crowns were allowed to listen to tapes of white-crowned sparrow songs, these birds started singing when they were around 150 days old. By the age of 200 days, the isolated birds not only sang the species-typical form of their song, they closely mimicked the version they had heard on the tape. This experiment showed that behaviour can be shaped by learning.