69. Just what is a “species”?
8. How Songs Change over Space and Time
Each species has its own song
From page 146 in the book.
Just what is a "species"? Ornithologists face one dilemma after another when they try to answer the question "Do these birds represent one or two (or more) species?" We come to take field guides as gospel, but lurking behind so many of the species illustrated there are these kinds of species conundrums. Here is a short list of some field guide species for which ornithologists wonder whether they constitute two or more different species. As you travel, listen up! How do the sounds of these species vary geographically?
Red-shouldered hawk
Red-tailed hawk
Northern flicker
Olive-sided flycatcher
Bell's vireo
Common raven
Purple martin
White-breasted nuthatch
Brown creeper
Marsh wren
Bewick's wren
Swainson's thrush
Hermit thrush
Purple finch
Evening grosbeak
Savannah sparrow
Fox sparrow
White-crowned sparrow
Dark-eyed junco
Orchard oriole
Common yellowthroat
Yellow warbler