We've lived here for 20 years but have never seen this before. We have an outdoor fan on our front porch. As I was spring cleaning my house in April, a mess on the porch floor outside the window caught my eye.
After watching for a bit, I discovered the culprit. A Robin was bringing pieces of dead decorative grasses from the neighbor's yards and laying them on the fan blades. Most of them fell off onto the porch floor much to my indoor cat's delight.
I was concerned that this Robin was not very bright since it seemed no progress was being made. I did not appreciate the Robin bringing yard waste from the neighbors who had not cleaned up their yard as we had. She kept at it and eventually a pile formed on one of the fan blades.
She then brought little clumps of mud in her beak, placed them carefully inside the forming nest and pushed them into place with her chest. Sort of shimmying to smooth it out.
In two days, the nest was finished. I saw her lay her eggs in the nest the next day in an odd arching movement. That was about ten days ago.
It turns out that she is quite clever and we the ignorant ones.
She frequently leaves the nest for short periods of time. We comment that she's gone for coffee or is taking her lunch break.
She watches TV through the window and is very aware of the cat watching her from inside. The Robin closes her eyes and sort of tucks in to sleep at night.
We look forward to the hatching and watching her feed the babies. We will remove the nest at the end of the season per the advise from this site.