Most of our migrant and wintering Savannah Sparrows are likely of the form savanna which is the one that breeds closest to New Jersey, in the NE USA. There are at least two other forms that are pretty much identical to this as far as field observations are concerned so it's hard to be 100% sure. However, come late fall and winter, a walk along the dune edge at the back of Cape May's beaches could find you staring at something that doesn't look quite right. A frosty gray creature runs like a mouse through the open grass clumps; eventually you glimpse the bird and a better view reveals something that looks pretty odd.
You've just found yourself an Ipswich Sparrow, the form princeps of Savannah Sparrow, but a form that's a little special, as it winters in Cape May in only very small numbers (perhaps as few as 10-20 in the county each year) and indeed has an amazingly small world range. Ipswich Sparrows breed exclusively on Sable Island, a 22-mile long spit of an island which lies over 100 miles out into the Atlantic Ocean from the Nova Scotia coast. They leave the island in the fall and spend winter scattered in small numbers from Nova Scotia, south down the Eastern Seaboard of North America. The entire population is believed to number less than 6000 individuals (perhaps around 2000 breeding pairs each year) so you can imagine that such a small number scattered down the entire eastern coast makes them pretty thin on the ground! Such a globally scarce population will always be vulnerable to environmental change, though at present there are not believed to be any specific threats to this bird and habitat on Sable Island currently remains in good condition.
I chanced across two Ipswich Sparrows on the South Beach at Cape May on November 22nd and saw another one today. So give them a look, but do be careful as their preferred habitat is very vulnerable to damage. Here are some pointers to the species identification.
Here's a 'regular' Savannah Sparrow, photographed at The Nature Conservancy's Migratory Bird Refuge recently. Note the overall brown tones and the rather thick and smudgy streaking underneath. On many birds (as here) the yellow patch on the supercilium, just in front of the eye shows reasonably well.
This Ipswich Sparrow, photographed on Cape May's south beach, shows much finer streaking below, broad, pale gray edges to the upperpart feathers, giving a rather 'frosty' look, and a very weak yellow patch on the supercilium. Many birds have a reddish or even pinkish tinge to the brown streaking, especially below.
Seen from behind, the grayish wash on the upperparts is most apparent - especially when you see them flying away!