First thing I had put on my chimney was a cap cause I kept having birds show up in the fireplace & then chased around the house to get them back outside. I am surprised mine has stayed in in some of the 80mph winds we have had. I have a double chimney. One flu into the basement fireplace & one for the family room fireplace right over it. Lol.... I understand your wondering what was going to fall out of there.
Glad I had the cap on when I had the trees close to my house & saw raccoons up there a few times. They never touched the roof guess just exploring. Never know what we might be up there.
I can't use my family room fireplace until the cement around the fire box gets repaired. Found chunks of cement inside the fireplace & can see where they are breaking off from