Both spikes and loose nets can be installed over nest sites to prevent the bird from returning, but nets are not a humane option since birds and other wildlife can get tangled in them. 

Spikes are a humane alternative that deter nesting without harming the birds. In small areas, like vents, a very fine mesh net can be installed to prevent the bird from returning. These nets don't generally pose a risk to the birds.

Keeping your pool cover clean is a good way to keep smaller animals from running across it or using it as shelter. Small animals may use leaf debris on top of the cover to hide. Cleaning also removes nuts that may fall from a nearby tree that could otherwise be a tempting snack for some animals, like squirrels. 

They can have a deterrent effect on birds to some extent. The reflective surfaces of these objects, such as aluminum foil strips, CDs, or reflective tape, create flashes of light and movement that can startle or confuse birds temporarily. However, some birds can become accustomed to these visual disturbances over time and might adapt their behavior accordingly. For a more sustained solution, combining shiny objects with other deterrent methods shared here is often beneficial for creating a more comprehensive and effective strategy for bird control.

Certain strong smells may help repel bats, though this is not a foolproof method and is best used in conjunction with other deterrence strategies. Scents like peppermint oil, eucalyptus, cinnamon, cloves, and mint are often suggested as natural remedies. To create a spray, you can mix two cups of warm water with half a cup of sugar and a few drops of your preferred essential oil. Apply this mixture using a spray bottle to possible entry points and throughout the affected area, such as an attic. While this home remedy is popular, evidence supporting its effectiveness is limited.