With the first frosts of fall, my garden turns from a lovely shade of green to a dirty brown with withered sticks and leaves. While my first inclination is to clean up everything, there may be seeds that you can collect or even save for the birds.
Here’s a good video which talks about some of your options.
Butterfly Gardening 
We leave that dirty brown withered stuff–most of it anyway–because the birds eat those seeds. Watching them on feeders is fun, but watching them dangle upside down to get a Goldenrod seed is even more interesting.