The song of a deafened bird is even cruder than that produced by the isolated bird because although the deafened bird may have an exact template, it cannot hear its own output, so it cannot compare the song that it sings with the internal template. The white crowned sparrow may be unusual in having a sensitive period for memorization that is over before the bird itself begins to sing. Other birds may show a longer period during which they learn a song. The young bird does not sing, but the model is remembered for two months or more The maturing male begins singing its sub song at about 150 days of age. The bird cannot learn a dialect.
Vocal output develops to match specifications of the unimproved template.
The bird cannot learn a dialect. Vocal output cannot be matched to the unimproved template. Summary of development of bird song. Marler's experiments clearly show the interaction between innate and environmental factors. Sparrows have dialects.