The Purple Finch is one of our best warblers. Let me unpack that. A "warble" is a jumble of
dissimilar notes, produced too rapidly to count. That's my on-the-spot definition and it is
informative, but not part of a system. For a taxonomy of sounds, let's go to Nathan Pieplow's
introduction to birds sounds, specifically to page 7 in both of his guides. A note is a
continuous sound, i.e., a single trace on a sonogram. There are five pitch patterns for notes:
flat, up, down, cupped, and saucered. Notes are combined. There are only four kinds of combinations.
Repetitions of similar notes at a rate slow enough to count are series, repetitions too fast to count are trills.
Countable sequences of dissimilar sounds are series. Sequences of dissismilar notes too fast to count are warbles.
There you have it: the definition of a warble. Many people have used these terms before. No one, to my knowledge,
has systemitized them so completely and comprehensively. I dare say Pieplow's system could be applied successfully
to all the bird sounds of the world.
By this defintion, the Haemorhous finches (e.g., Cassin's) are stellar warblers,
as is their close relative the Pine Grosbeak. Warbling Vireos
(East and West)
do indeed warble, although no other northern vireo does. No North American wood-warbler warbles, except
perhaps the Red-faced Warbler. The same goes for the New World Sparrows, except for the genus Artemisiospiza , which
does a buzzy sparrow-warble.
The breeding range of the Purple Finch wraps around that of the Cassin's Finch. The eastern Purple Finch, a bird of the boreal forest, sounds a little different. Below is an eastern song
to compare with the western song above.