The last definite known individual died on Walt Disney World's Discovery Island in 1987,[3] and the subspecies was officially declared extinct in December 1990.

[4] Its dark coloration[5] and distinct song,[5][6] which is introduced by a buzz rather than the discrete clicks heard in Ammospiza maritima mirabilis[7] and has been described as "insect-like" by ornithologist William Post,[8]: 97  distinguish it as a subspecies from other seaside sparrows.

[12]: 851–852  When Merritt Island was flooded with the goal of reducing the mosquito population around the Kennedy Space Center, the sparrows' nesting grounds were devastated, and their numbers plummeted.

[13] By March 31, 1986, further breeding attempts had failed, and of the four dusky seaside sparrows originally brought to Discovery Island, only "Orange Band" remained.

Despite being blind in one eye, "Orange Band" reached an extreme old age for a sparrow, living at least eight years, and possibly as many as thirteen, before being found dead on June 17, 1987.

[15] In the hopes that cloning would someday give scientists another chance at saving the subspecies, the heart and liver of "Orange Band" were cryopreserved,[16] and his body was preserved in alcohol at the Florida Museum of Natural History.

Unfortunately, shortly after the breeding program was halted, the remaining hybrid sparrows either died or escaped captivity, leading to the final extinction of the taxon.