The Saltmarsh Sharp-tailed Sparrow is nonterritorial and promiscuous, and only females provide parental care. Males occupy large overlapping home ranges, and the mating relationship features forced copulations by males.
Breeding success in many Saltmarsh Sharp-tailed Sparrow populations seems limited by storms and especially â€œspringâ€ (high) tides, which often flood nests. The most successful pairs in these populations are those that renest soon after the flood tides of the new moon.
The Saltmarsh Sharp-tailed Sparrow formerly was considered as the same species as the Nelson's Sharp-tailed Sparrow, collectively known as the Sharp-tailed Sparrow. The two forms have separate breeding ranges that barely overlap in Maine. They differ in genetics, songs, and subtle plumage characters.
The oldest recorded Saltmarsh Sparrow was a male, and at least 7 years, 11 months old when he was recaptured and rereleased during banding operations in Rhode Island.