(Also pictured (bottom): Cape Sable seaside sparrow (Ammodramus maritimus mirabilis), FMNH no. 178376; conservation status: endangered)
Declared extinct in 1990, the Dusky seaside sparrow was one of 11 Ammodramus subspecies to inhabit the coastal marshlands on the Atlantic seaboard of the United States. A. m. nigrescens was non-migratory and lived only in the marshes of the St. John’s River and Merritt Island on Florida’s mid-Atlantic coast. A 70 percent decline in population was recorded from 1942-1953, following the use of the insecticide DDT to control mosquitoes on Merritt Island, which contaminated its food supply and caused thinning of its eggshells.
In further efforts to eliminate mosquitoes in the Kennedy Space Center region, in 1956 the Merritt Island nesting grounds were flooded to make mosquito control impoundments, causing another drop in numbers. Later, marshes along the St. John’s River were drained to aid highway construction, putting yet more pressure on the population.
By 1980, six remaining individuals, all males, had been captured to establish a captive breeding program that was eventually unsuccessful because no females were ever found. They lived out their lives in a Walt Disney World nature reserve called Discovery Island. The last male died in June 1987.
The Cape Sable seaside sparrow is a one of eight remaining species of seaside sparrow and a subspecies of the Dusky seaside sparrow. It is native to the prairies of the everglades on Florida’s peninsula. The large-scale conversion of south Florida for agriculture and its limited range mean that the Cape Sable sparrow is currently endangered. It is also threatened by fires, hurricanes and the alteration of water flow in the area – any of these could cause a catastrophic drop in numbers making the population non-viable, meaning the birds would not be able to reproduce quickly enough to increase their numbers. Efforts to ensure the birds have the right amount of water have resulted in the Everglades Restoration Transition Plan to improve conditions for the sparrow and save it from impending extinction.