THE SECOND NEST. This is at a tree trunk that's within 100 meters east of the first nest. This nest appears to be built also of mud, and likewise about 15 meters high from the ground.
Its entrance hole is facing northwest. One of the nesting Guaiabero couple is shown here inserting its head into the nest. I wasn't able to see whether it was feeding, or it was just building the nest.
I had to use the hand held 20D + 500 f4 IS + Canon 1.4x, as the 350D + Sigmonster together with my tripod/gimbal head was set up near the first nest.

[20D + 500 f4 L IS + Canon 1.4x TC, hand held]