Having covered Nelson's Sparrow earlier this month, today I'll cover the other former "Sharp-tailed Sparrow" known as the Saltmarsh Sparrow.
Saltmarsh Sparrows breed in coastal New England marshes as far north as southern Maine. Though similar to Nelson's Sparrow in appearance, Saltmarsh Sparrows have a yellow bill and distinct chest streaks (vs. the blue bill and blurred streaks of Nelson's). Observing these differences is not always easy, and as I warned in my previous post, hybrids of the two sparrows may show a blend of characteristics that make definitive identification impossible.
In my experience, Saltmarsh Sparrows sing more softly than Nelson's. The bird in the following sample recorded by Tayler Brooks at the Scarborough Marsh sounds louder than any I've heard in person: