IN likely the most bizarre summer sighting and given the location, an immature COMMON MERGANSER was spotted by Rob Bate in the early afternoon. I came after Rob's tweet and saw the bird as well. Ambergill Pool is not known as a duck spot ( except for Mallards) because of its tiny size. But to see something like COMMON MERGANSER now and in that location is truly way out of line for the season.
ON the mostly brownish bird, we could see the whitish line mark below the long mandible, ( not red for similar Red-breasted Merg), breast/ neck was brownish ( dark) not white for RB
from google searches, closest resemblances are below
http://newenglander.smugmug.com/Travel/Florida-Miami-MetroZoo/Miami-MetroZoo-August-12-2007/i-K892gLs/0/L/135%20Common%20Merganser%20%28Juvenile%29%20-%20August%2012%2C%202007-L.jpg
next photo see rightmost bird
http://whatbirdisthis.files.wordpress.com/2012/08/juvi-mergansers-whistler_bc.jpg
KB Note: Only other August Merganser sighting occurred Aug 31st, 1997 when a hen Hooded Merganser was spotted in the Upper Pool, then called Swan Boat pond.... ( R.Jett)