Mystery Bird?

The suet tray remains a popular addition to the Bon Bon Pond feeder arsenal.  The Blue Jays just love it, as does the Eastern King Bird.    But the “stand and eat” concept has brought in yet another mystery bird.  The photos below capture a solitary black bird at the tray.  My first thought was a Red-winged Blackbird as the eyes, beak and legs are all dark but I will be darned if I can find one bit of wing color.  Additional research into the species told me that juveniles are brown and streaked liked the females.  I have carefully observed this strange fellow and he always seems to be alone.  When he leaves the tray he wings off.  I have never seen him eat seeds or approach the traditional hanging suet cages as the other Red-wings do.  Also, my other Red Wings are always together in groups.  Further, , the tail doesn’t seem right for a Red-wing.  ???