[SBB] Black Tern in Salt Pond A16

At about 11:20 this morning Frank Vanslager and I had BLACK TERN on the first island in Salt Pond A16. Unfortunately shortly after we spotted the bird it made a short flight along the length of the island and upon re-landing it was immediately chased by an adult FORSTER'S TERN. The BLTE then flew west northwest across the pond and out of sight. We then spent the next 45 minutes checking out the remaining islands and pond perches without re-finding the bird. The Tern was much smaller than adult FOTEs, had a fairly uniform dark gray mantle and upper wings (no obvious hint of the brown that is usually seen in these areas on juvenile BLTE). The head was white with a black cap and "earmuffs," it had a short straight black bill, a whitish chest and belly. Unfortunately I never made note of the leg color (it was in a bit of a depression when first found). Note: We usually don't see juvenile BLTE until about mid August in the bay area. Unfortunately Sibley says that the earliest one would normally see basic plumaged BLTE would be in August whereas Juveniles may be seen as early as July. I personally have never seen an early juvenile without brown in the wings and mantle. Earlier Frank and I walked the railroad tracks through New Chicago Marsh, nothing new but there were hundreds of Phalaropes (WILSON'S and RED-NECKED), numerous small flocks of peeps (mostly LEAST but a few breeding plumaged WESTERNS included), a few Dowitchers and a couple MARBLED GODWITS. At one point a PEREGRINE FALCON attacked a flock of peeps nearby but by the time if locked onto one it had lost most of its momentum and was too far behind, it then gave up the chase flying east northeast out over Salt Pond A16. There were no Snowy Plovers in the Alviso impoundment.