Answer: Critters like to eat and from their point of view, you're providing a tasty meal! They get used to all the various "foils" so you need to keep applying and moving them.
From your description, I don't know what's eating your seedlings/seeds, but birds enjoy the young, juicy seedlings. You can try erecting bird netting over newly seeded areas, making sure it's high enough to allow growth and not let the birds poke through it. When the plants get more established, you can probably remove it.
Just about the only thing to prevent birds from getting at your fruit is netting, and alas, this isn't always easy with larger trees. There are the old standbys such as hanging aluminum pie pans from the branches, metallic reflective tape, wind chimes, and fake owls. These do work for some folks on some birds, especially if you keep changing and moving them about. You can also loosely wrap some of the fruit/branches in cheesecloth, netting, etc. to ensure you at least get to taste the fruit of your labors!
How to keep a squirrel out of a tree? That's a tough proposition. You can try baffles that prevent them from running up the trunk, or more bird netting. You'll have to secure it around the trunk so the squirrels can't get in. Depending on how low the lowest branches are, you could wrap a wide metal band around the trunk, just as the fruit is
ripening. That would prohibit squirrels from climbing the trunk. If the lowest branches are within squirrel jumping distance--or if there are other trees around that the squirrels could jump from, it wouldn't help. I'd try the
netting. Good luck!
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