I received the following off-list comment that makes a lot of sense 
to me. [I've left out the author's name because I assume if the 
author had wanted to comment publicly he/she would have replied 
on-list.]

    "On the pics that are not back lit it looks like the upper 
mandible is a bit overgrown.  If this is the case it's not that 
unusual (I saw a woodpecker one time with a really overgrown upper 
mandible)."

That would explain why the protruding feature appears most prominent 
in photos 1 and 2, which are the most back-lit. Since Wilde Lake is 
most conveniently accessible on the north side, most of my photos 
were shot partly into the sun. It so happens that photos 4 and 5 
were taken from the south side of the lake so that the sun 
reflections were minimized.

It also explains why the bill appeared slightly downcurved when I 
was watching the bird. I had wondered about that, since Sibley shows 
the bill of Red-necked Grebe to be straight.

June
__________________________________

June Tveekrem wrote:

http://junetvee.smugmug.com/gallery/4474008_4Bo74#263127873

-- 
June Tveekrem
Columbia, Maryland
tweekiebird|AT|southernspreadwing.com