While idly looking out the window, I spotted this Gray Squirrel (Sciurus carolinensis) heading up an oak tree with a mouthful of leaves.
Here is where the squirrel was headed. It is using the leaves to construct a “nest”. This nest obviously needs a bit of infill to make it snug so it has a few more trips to make. Although the nests look rather disorganized, they are carefully built. Their form is hollow and roughly spherical. The outer part is made of interwoven sticks and leaves and provides good protection against the elements. The inner chamber is lined with softer materials, such as pine needles, shredded bark, grass or moss. The entrance holes, usually two, are located on the bottom of the nest.
Gray squirrels prefer to live in hollow tree dens, but if not enough of these are available they will construct leaf nests similar to this one. They usually live alone, but females and their young will, of course, occupy the same nest. During mating season a male and a female may briefly occupy the same nest. The young squirrels will usually leave the nest for good when they are 10-12 weeks old.