For starters the bad news; you have both of the species of medical importance (
Loxosceles and
Latrodectus, recluses and widows) in your area. The good news is that verified bites are ridiculously rare, and the majority of the "brown recluse" bites reported are due to other common causes. Medical misdiagnosis of loxoscelism is annoyingly common;
the AMA has a position paper on it and there's more in the scientific literature basically chiding doctors for missing obvious differentials and calling it "spider bite" when it clearly isn't. Generic doctors aren't experts on envenomation, unfortunately, and in the US they seem to miss a lot more than they get right.
Due to the physiology and known behaviors of both spiders and chickens, I very seriously doubt that a bite to a chicken from either a recluse or a widow is likely. Spider fangs are teeny-tiny even in relatively large adults, and can barely penetrate human epidermis. Generally they need assistance to do so, being compressed between skin and clothing. They would have even more trouble with chicken skin and feathers, and animal fur, which is why genuine spider bites to pets and animals are extremely rare in the veterinary field.
A spider cannot make accurate determinations as to its bite target, other than in the prey it specifically evolved to eat, and when they bite at all they will bite at any presented object including a feather. I don't see a spider getting anywhere near a thin enough bit of epidermis to bite, unless it was taken into the mouth and swallowed whole without being pecked to pieces first. Even then, I don't see a bite as a very likely scenario as the spider is not going to be in an optimal position, or probably very functional after being snatched in a hard beak.
If you're asking if they are poisonous to consume, as opposed to being able to deliver a venomous bite, the answer is no, they are not. Birds are a major predator of spiders in the wild.
Spiders in North America that are not in either of those two genera are not medically significant (with the possible exception of hobos and yellow sacs, but that's a little dubious) and you can ignore them as they are incapable of harming anything bigger than a bug.
