To Kim Schmidt:
This s a really common issue, but most people don't take it too seriously until after they get their birds. I'm glad you're thinking about it ahead of time.
Our experience has been that once young chickens get used to where to go at night (usually just a few days), they put themselves into the roost at night. If you make sure your roost area is up off the ground, most predators won;t be able to get at the birds once they're in the roost. However... if you have weasels in your area, you'll need to have a door that closes on the coop. We also replaced the ramps going up into the coops with platforms about 18" off the ground; this was after a skunk walked up the ramp into the coop and killed two hens. They're bit pricey, but you can also install automatically-closing doors on the coops so you will know the birds are safe even if you aren't there to close them up.
Re: Ducks. I personally would not recommend the island, at least not as a place for the ducks to sleep at night. Ducks really like to feel safe and they hate stray light at night, so if you have traffic nearby or lights from houses,I would definitely recommend housing them in a coop at night. (Plus you get the eggs this way.) We have two large ponds on our property, and the ducks do go down to them sometimes, but they always come back up the hill to their coops at night. You could always put a coop down near your pond too. Caveat: If you are going to use a coop, train your ducks to go to it at night BEFORE you let them get used to being on the pond all day. Trust me, ducks know where they feel safe, and once they're used to being in a coop at night, that's where they will want to be.
We have been raising heritage turkeys for about 6 years now. Most of our property is woods. Heritage turkeys are usually good foragers, but I would not encourage you to try to leave them on their own to forage all their food. Turkeys, even smaller ones like our Midget White, are large birds that need a lot of protein for best growth. Certainly if you are planning to raise turkeys to slaughter for meat, you'll get a lot better results if you give them a good high-protein turkey ration; if you can't turkey feed, some people substitute game bird feed. They need 24-28% protein feed for the first 6 weeks or so, then at least 20% from then on. Our turkey "grower" formula is 21% protein.
Once they're at least half grown, heritage turkeys are large enough that they don't have too predator issues. In our area, we have only ever lost an adult turkey to a cougar. On the other hand, we don't have coyotes or neighbor dogs here, and they may be a problem for you. I would recommend that you do not clip their wings, so they can fly up into a tree if they need to. We never clip our turkeys' wings, for this reason.
I would definitely recommend starting out small, figure out what works well for you, and then add more birds as you find you have the time and comfort zone to do that.