Welcome!! You need to secure your run as if you DO have predators. Cats, raccoons, opossums, fox and even coyote are all around urban and suburban areas. Most of us can tell you of a loss or too. I had a loss to a hawk just a few weeks ago. Do what you can to protect them.
I would research the toxicity of the variety of crab apple it is. Apple seeds can be toxic to Chickens but I don't know about the crabapple.
You are only a few minutes from my town (Moorestown, NJ), and there ARE definitely hawks and possums! We made our run all with chicken wire and wood - in a year, nothing has got into it. I let the chickens free range the backyard if I am home and can keep an ear/eye out. (We lost a silkie last week to a hawk during free range though.) I don't know about the crab apples. Sorry!
Thanks for the info and suggestions. We too had plans to do a little free range for the girls as well ( of course when we are out there). I am hoping that our dogs will help to be a little extra protection. I will look up what info I can on the crabapples. The trees where here when we moved in and my husband has been looking for a good reason to take them down. They really are a pain in the ***** they are only about 7ft tall total so it make mowing the lawn for a 6ft 4 in man hard and they drop stuff year round. So he may get him wish
Thanks again, Ill let you know how it goes