Grassquit

1988 [1948], David Lack, Notes (for 1988 edition), Darwin's Finches, page xv, Steadman (1982) suggests that Darwin's finches are so closely related to the South American blue-black grassquit (Volatinia jacarina), that all 14 species plus the grassquit should be considered congeners within a new genus, Geospiza.

The molecular work also makes a compelling case that Darwin's finches were originally grassquits.

The current guess is that it was the wonderfully named dull-coloured grassquit, because this is the bird with the closest genetic code to the Galapagos finches.