Sparrow ID please, New Jersey, December - and Banded

Photo taken at 4pm, 12/31/12 in Alpha (Northwest) New Jersey. Note that the bird (sparrow, I assume, right?) has been banded. Why? Is he special or something?

There were just a couple of these birds feeding in a grassy field on the ground. They were seen near -- but not co-mingling with -- a flock of Horned Larks. I don't think I got a good shot of his front/breast, but I'll double check and post, if so.

Thank you in advance.

this is a Savannah Sparrow. streaked underparts are clearly visible as is the coarsely streaked back. fairly strong pale supercilium and malar. Among the features that help differentiate from Vesper Sparrow are the short tail, lack of a pronounced eye ring, and the brown wing panel on the greater coverts and tertial edges--a great mark for Savannah that isn't highlighted in the field guides. The yellow supraloral spot is, I think, overrated as an ID feature--it's often inconspicuous to absent, although it's great if it's there.

Thank you so much, Brian!