With the death of the last individual of the species, the dusky seaside sparrow becomes extinct.
The dusky seaside sparrow (Ammospiza maritima nigrescens) was a non-migratory subspecies of the seaside sparrow, found in Florida in the natural salt marshes of Merritt Island and along the St. Johns River. The last definite known individual died on Walt Disney World's Discovery Island in 1987, and the subspecies was officially declared extinct in December 1990.