in order to attract birds, we have a small bird house feeder that can be easily accessed by the birds, but is also within sight of our living room windows, so we can birdwatch from the indoors, too. we usually feed them sunflower seeds, but we have also made bird feed ourselves from unsweetened peanut butter mixed with oats and seeds, and it was very popular with our feathered friends.
just a couple of weeks ago, noticing that the birds started collecting building materials for their nests early this year, we filled mesh bags with bits of yarn, straw and dog hair which we got from friends with a dog. (we used cotton mesh bags that used to hold apples from the grocey store, but you can also make a small basket using coated florist wire to hold everything together). we placed the nest building stations at spots that are easily accessible for small birds.
the chickadees especially loved collecting materials for their nests on our terrace. when we go nest hunting in autumn, we will be looking out for nests that have some of "our" yarn worked into them!