For those of you who wish to skip the slightly graphic nature of the post, here's the summary in advance:
Only put out dryer lint as nesting material IF you do not use dryer sheets. EDIT: please see comments for discussion!
Cut materials (string, yarn, hair) into pieces smaller than 2 inches long.
Clean feeders thoroughly and frequently.
...and back to the post:
If you want to supply nesting materials for birds, please take note!
Dryer sheets are toxic. (That's four different links, beware!) So while 'plain' dryer lint is a great idea [edit: for cavity nesters only - exposed nests would then absorb water), if you use dryer sheets, do not put out lint. The chemical residue in the lint will be touching the skin of naked baby birds; if it's toxic to adult cats and dogs to ingest, rule of thumb is that it is more toxic to a naked baby bird.
So you cut your hair? Have some scraps of yarn? Found some string? Great!
Cut it up.
Cut it into pieces shorter than two inches.
Many young birds never leave the nest. The above Barn Swallow would have fallen from the nest (perhaps lived, even), but its wing was trapped by a hair. Mule tail hair, but hair nonetheless. And as you know, fishing line kills adult birds as well as baby birds - but yarn, string, and hair can wrap around a baby bird's leg/wing/neck. We've untangled a yarn-heavy nest in the past to free a House Finch who lost a leg due to lack of circulation... it's more common than you'd think.
And for the cleaning portion of the post:
I'd like to devote a bit of blog space to cleaning bird feeders; it seems in line with our 'do no harm' mantra. Dry feeders should be cleaned monthly at the very least (more often as needed), but it's incredibly important to know that the task is not simply for aesthetics. It's for health. Conjunctivitis (pink eye - in birds appears as a redness with crusty goop accumulating around the eye) is quite common in House Finches and having large flocks at feeders in winter translates to a lot of children eating at a buffet; you want to clean EVERY utensil thoroughly after they're done! Left uncleaned between the winter rush and spring, you end up with young birds who are being fed from contaminated sources. Every winter in college, I was brought at least one or two young House Finches who should have fledged normally but ended up with conjunctivitis. It's treatable once the bird is in rehab, but I suspect that most never make it to rehab. Hummingbirds and their liquid diet are a bit more prone to buildup of contaminants, so cleaning them every few days is absolutely crucial. Especially in the summer heat, it's far better to put out a partly-filled feeder than wait for the level to go down!
A few links to get started with feeders:
Keeping feeders clean - from Wild Birds Unlimited
Feeder cleaning tips from about.com
Cleaning feeders on ehow.com
...it's even in the ABA Code of Ethics:
3. Ensure that feeders, nest structures, and other artificial bird environments are safe.
3(a) Keep dispensers, water, and food clean, and free of decay or disease. It is important to feed birds continually during harsh weather.
3(b) Maintain and clean nest structures regularly.
3(c) If you are attracting birds to an area, ensure the birds are not exposed to predation from cats and other domestic animals, or dangers posed by artificial hazards.
...and as a thank-you for reading, here's a healthy, happy nest of Barn Swallows!
That's Gladys the female leaving and Gladys the male showing up with a bug for the three little Gladyslings. (From See Trail's "Busy Parents" post - July 2010 in Marathon)