It's been downright soggy here and the whole darned yard is basically now a mushroom farm. There are a lot of different small varieties and also these three different huge fungi all on the same tree.
We had carpenter ants on the same huge tripartite oak in early September, and Ryan from SavATree reassured me that it's not necessarily a sign of decay. However, he said to keep an eye on this cleft between two of the trunks. If it gets bigger, we need to worry. (Meanwhile, being me, I guess I'll just worry that it will get bigger.)