A recent post by Jeffrey M Harris described a black-capped chickadee feeding a nest of robins.  There has been  some follow-up discussion. While not as unusual of the chickadee and robins, I  posted some photos of a common  yellowthroat feeding a brown-headed cowbird here:

http://www.jimblockphoto.com/2012/05/yellowthroat-feeding-cowbird/

Jim Block

Etna, NH