I spent some time this morning in Forest Park, St. Louis, where nest building is under way. The house I was watching is along a small waterway and the birds gather dead grass along the water's edge, often pulling it out of the mud.
This morning I saw a pair of martins in the limbs of a nearby tall cypress tree, making great effort to strip bark from limbs. Both the male and female put quite a lot of effort into this on the interior limbs of the tree, which is just beginning to bud out . Only once did I actually see one of the martins, the male, manage to rip off a long shred of bark and carry it back to a gourd that hangs below the house. When I do a nest check I'll inspect this one more closely to see if it's mostly made of cypress bark.
John Miller
Unusual nest building behavior
John, I offer all sorts of materials for the PMs when nest building, but they are picky and select what they want. I watched on pair pull and tug on a grass blade for 15 mins. with raked up rows of dead grass, pine needles, corn fodder, fresh dead leaves, and small twigs with a foot of that blade of grass they wanted. I also observed that some wait in ambush and try to steal what their neighbor has picked up. Kind of comical to watch especially when the squabbles break out.