Guam's forests would not necessarily look like Swiss cheese without birds. While birds do play an important role in seed dispersal and pollination, there are other factors that contribute to the health and structure of forests. Here are a few reasons why Guam's forests might not resemble Swiss cheese without birds:

Other seed dispersers: Birds are not the only animals that disperse seeds. Mammals, such as bats, rats, and monkeys, also play a significant role in seed dispersal. In addition, wind, water, and even gravity can disperse seeds.

Plant adaptation: Many plants have evolved adaptations that allow them to disperse their seeds without the help of birds. For example, some plants produce seeds with wings or parachutes that allow them to be carried by the wind. Others produce fruits that are eaten by animals, and the seeds pass through the digestive system and are deposited in new locations.

Forest resilience: Forests are complex ecosystems that are able to adapt and recover from disturbances. Even if birds were to disappear, forests would likely still be able to function and maintain their structure. Over time, other species might evolve to fill the ecological niche left by birds, and the forest would eventually reach a new equilibrium.