From YardMap‘s Facebook page:
In an increasingly fragmented and anthropocentric landscape it can be difficult and time consuming to locate enough high quality building materials to make secure and well insulated nests.Many birds will resort to using dangerous materials like plastics, garbage or even cigarette filters. Leaving out piles of natural building materials will help provide birds the supplies they need as well as saving them time and energy that is better spent building, incubating, and raising their young.
Offer broken-up sticks of different sizes, wool or cotton batting, feathers, coconut fibers, untreated animal fur, horse hair, moss, mud in a bowl or puddle, even spider webs and snake skins!
Check out our nesting materials Pintrest board for more ideas: https://www.pinterest.com/cornellyardmap/offer-nesting-materials/
For excellent nest information and an opportunity to take a very active part in the nesting going on in your yard visit: nestwatch.org.