Did you know.. Some birds use animal fur they find in nature to line their nests. It provides a soft surface for the nestlings as well as acting as an insulator from cold and wet. You can help those birds by providing fur from your dog or cat. By doing so, you might help their nesting success as they conserve energy by taking advantage of an easy source of animal fur. However, you should not use any type of animal fur that has been exposed to flea or tick treatments.
If you have a dog ( or cat) that requires alot of brushing, instead of just throwing it away in the trash.. open up the door and throw it into the wind. The birds will find it and use it for interior insulation during these cold winter days and nights.
Heres some other items you may not want to dispose of so quickly :
Pine straw, wheat straw, and tiny twigs make good bird nest building materials....
You can also use human hair clippings, too. Just don't use any hair or fur that's been treated with chemicals, such as hair dyes ( flea dips or insect repellents)
Note: While it may seem like a good soft insulator. Lint from a clothes dryer is bad, bad, bad. Chemical softners and perfumes can be extremely harmful to small birds.