Kind of butting in to this conversation (sorry) but want to mention something about bird nest-building materials I just read this morning -- can't remember where. It cautioned against putting out cat or dog hair for the birds if the pet is treated with anti-parasite chemicals. It also said dryer lint is NOT good either -- It retains wetness, and the laundry detergents/softeners are also harmful to birds. String, yarn, etc. can wrap around bird legs and trap them or cause circulation issues or even amputation. This source concluded by saying birds don't need our help finding nesting materials -- the natural world of leaves, weeds, grasses, etc. provides plenty!