Dead branch on Oak Tree - bark gone black holes
I have a white swamp oak that is about 15 years old and this year all the leaves on one of the lower branches have died. I looked at it closer and the bark was removed and there are black holes in the branch. There is a squirrel's nest up higher in the tree. What can I do for my tree?
I think this is an issue for a professional arborist.
For sure you have one large dead branch. What its removal will do to the structure and aesthetics of the tree I can't tell from your photo. The squirrels' nest may be more of a consequence of the dead branch than a cause. I am not sure what caused the damage to the bark on the branch. Nor can I tell from the photo how extensive the decay in that branch is.
Finally, while the danger time for pruning oaks has past (April to June), some oak wilt insect vectors are still around, so, if possible, pruning should wait until late dormancy.
All of these issues can be resolved by a certified arborist:
Here is a DIY diagnostic site (although I still urge you to get a pro to look at your tree):