Barbara Ballentine, a postdoctoral fellow with the Smithsonian Migratory Bird Center, is investigating the differences in song between 2 subspecies of the swamp sparrow.
The inland subspecies, which breed across Canada and in the Appalachians, tends to have a more musical and complicated song than its relative that breeds from coastal New Jersey to Delaware. In the sonagrams below, which are a visual representation of the songs, note the thicker and longer lines of the inland songs. These are likely more difficult to sing.
The differences in song may be attributable to a difference in bill size. Coastal birds tend to have larger bills and may have a more difficult time maneuvering their bills quickly to sing a complicated, musical song.
Genetic studies indicate that the subspecies of swamp sparrows have been separated for about 10,000 years. In addition to the differences in bill size, coastal birds also tend to be darker in plumage and have a different nesting strategy. They may be evolving into different species.
Below are 2 examples of inland songs and 3 examples of coastal songs. As you listen to them, can you hear any differences?
Did you know that female swamp sparrows chatter every time they leave the nest? This would seem to be a dead giveaway to any nest predators. Find out why they do this.