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Are the yellow edges of this plant's leaves a new occurrence, or has it always had this leaf coloration? I ask because the leaves look like variegated holly varieties that naturally have white or yellow leaf edges, for example in the following photos. So the yellow is probably normal.

The black spots, on the other hand, are likely a disease. These articles describe holly leaf spot diseases and what to do about them:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-problems-holly-leaf-spot-or-holly-tar-spot.htm
https://ag.umass.edu/fact-sheets/holly-leaf-spot

If leaves are falling off in patches, it could be this:
https://www.rhs.org.uk/advice/profile?PID=175

Scale insect attack is one possibility. This is an insect that can cause the leaves on one part of a holly (or several other shrubs) to turn brown and fall off:
https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm

Environmental damage such as scorch can also damage one side of a shrub. In this case pruning off the dead branches will fix the problem.

Also check this article for diseases affecting holly:
http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2054.html
https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm

I purchased a holly plant this fall. It has some berries, will work on pairing up this spring. However, my dilemma is do I bring it in for the winter or leave it in outdoors? I live in Minnesota and it cant get to minus 20 to minus 40 or so. If I need to bring it in, at what temperature? We may get frost this weekend. I still have it in a pot. Advice would be helpful.

They can start out this way, but they should mature into a red color. If they don't then this could be a fertilization issue. First, add dolomitic lime to the soil, and then fertilize with an all-purpose fertilizer.

Here is a link to more information: https://www.gardeningknowhow.com/ornamental/shrubs/holly/fertilizing-holly-bushes.htm

It is unusual for birds to eat a significant amount of plant foliage, although many birds will eat holly berries. They may have been looking for insects (and maybe they ate them all so you don't see any now). Possibly they were looking for bark or twigs to use as nesting material. Many mammals will eat shrubs, including the leaves and twigs, and mighttake of bark.

You can protect your bushes with netting if you do think it's birds that are doing the damage.

https://www.gardeningknowhow.com/edible/fruits/fegen/protect-fruit-tree-birds.htm

It would not hurt anything to do so. I don't see a problem with it. In fact, that will probably look pretty neat.