Wintering distributions and migration of saltmarsh and Nelson's sharp-tailed sparrows

We delineate the winter distributions of the five subspecies of Saltmarsh Sharp-tailed (Ammodramus caudacutus) and Nelson's Sharp-tailed (A. nelsoni) sparrows, and comment on patterns of migration. The two subspecies of A. caudacutus (A. c. caudacutus, A. c. diversus) have similar core winter ranges that extend along the Atlantic coast from North Carolina to northeastern Florida. They also occupy two isolated areas within peninsular Florida in Everglades National Park and on the northwest Gulf coast. Migration in A. caudacutus is mainly confined to the coast. The subspecies of A. nelsoni (A. n. nelsoni, A. n. alterus, A. n. subvirgatus) occupy different but overlapping winter ranges. A. n. nelsoni is the most widespread, occurring from North Carolina to Texas. Some birds migrate along the Atlantic coast southwards in fall, and others follow interior routes through the Mississippi River watershed in both fall and spring. We suggest A. n. nelsoni wintering along the Atlantic coast in spring fly directly inland towards their northern breeding areas. Some birds in fall also approach the southeastern coastline directly across the Appalachian Mountains. A. n. alterus mainly winters along the southeastern Atlantic coast to Florida, and in fewer numbers along the Gulf coast at least to Louisiana. Some A. n. alterus may migrate to the Gulf coast directly via inland routes west of the Appalachian Mountains. A. n. subvirgatus has the most limited wintering distribution, from South Carolina to northeast Florida, and is strictly a coastal migrant south of New England. Limited wintering ranges and narrow winter habitat requirements place continental populations of sharp-tailed sparrows at risk.