Wildlife Spotting

At first glance I thought bird's nest too but you can see the new fresh growth as stated below..very cool. My husband installs drywall and just did a job in a garage ceiling and found a really great plant that had grown up the wall between the drywall in the garage and the house. It was living beautifully under there and appeared to have been doing so for years based on the old dead areas and the new growth. Was making quite a mess out of the foundation and the drywall.

This is just a very strong running grass that grew up the inside of the hollow post of the street sign (aided by the holes in the post to add light and air) and is now expanding into the open space. I't's not Bermuda Grass (which also does this), but something with a thicker stem. I call it Bermuda Grass on Steroids.

Not a birds nest, they take a while to build their nests, the grass blades would be dry, not green. Someone probably stuck a clump of grass on the top of the sign, maybe to make it look like a nest.