Thursday, December 22, 2016
If It's a Common Bird, Make Sure It Has Attitude: Song Sparrow at Yachats, Oregon
The many subspecies and regional differences are emblematic of how evolution proceeds. The birds are common and widespread, but encounter different environments at the margins of their range. These different habitats favor different adaptations, such as size or coloration, or different food preferences. If populations become isolated, they may become differentiated enough to be classified as separate species.
If you've ever wondered about how Darwin's 13 species of Galapagos finches came about, or the 56 species (living and extinct) of Honeycreepers of Hawai'i, then these very common North American birds provide some insight. Variation is the key to evolutionary change.