If I could add my two cents worth to the speculation on the hanging nests...

I've been an avid nest hunter since the early 1970s. What's curious
about the original posting is that the nests are so close to the water,
and that some occurred in clusters.

Bushtits and orioles do build hanging nests, but not in groups, and not
that close to the water level.

Does the water level vary much in this lake? I know that when I started on
my obsession with finding nests, I was often fooled by clumps of debris
that got caught in willows and other streamside vegetation, during times
of higher water. They looked like hanging nests.

Mike Donahue
mdonahue at u.washington.edu