Adisease resulting in the deaths of one third of a dense population of bats in a cave would be a

A disease resulting in the deaths of one third of a dense population of bats in a cave would be a density-dependent limiting factor.

The density dependent factor are those factors whose affects on the growth or the size of the population can vary with the population density. Different sorts of density dependent limiting factors exist, for example: disease, migration, predation, availability of food. The last one mention is the main factor  that could result in death, for instance in the death of a population of bats.

the tallest building in the western hemisphere and the sixth tallest building in the world

thing is, i'm afraid, you can't.

the most you can do is log out and never log in again.