After vegetation improved in some empty lands in California, Oregon and Washington, during the last three decades, a scientist named Derryberry noticed a lowered pitch in male white-crowned sparrows. She also discovered that the birds slowed down their singing.
This is the first time that anyone has shown that bird songs can shift with rapid changes in habitat. Derryberry performed a comparative analysis of recordings of individual birds, which were made in 15 different regions, and some old recordings that were made in the same places back in the 1970s.
She discovered that both the musical pitch and the warble of the sparrows' short songs significantly lowered. She also include that she was surprised to find that songs had changed in a similar way in so many different populations. She found that in the areas where the foliage did not change, the songs of white-crowned sparrows hadn't slowed down. This means that with the alterations in the foliage songs will become slower and have a drop in pitch.
Derryberry's research adds more evidence to the belief that animals change their acoustic and visual communication depending on the habitat.
