It seems as if the birds are finding all they need to eat in the preserve. Do any of them grab a snake from time to time? Conversely, snakes and even squirrels can snatch a bird's egg from a nest. That's nature for you.
I've seen a number of bird feeders or pictures of bird feeders that can easily be attached to a fence or railing. Google 'bird feeders' and I bet you'll see some pictures that will inspire you. DIY plans abound.You do need to know what kind of birds that are around and that you'd want to feed. Some like to perch, some like to eat from tube feeders, etc.
All of my feeders are down right now. I've got to clean and sterilize them. When we had a turn in the weather a few weeks ago all of the feeders got moldy. Ick.
