Most people when you mention CCTV systems automatically think about the security of their property and garden but another much more enjoyable reason to have CCTV installed at your property is to watch the wildlife visitors that appear in your garden at night and also in the daylight hours when no one is around to disturb them.
When you are siting the cameras think about the areas that might attract birds and animals such as feeding stations and ponds and water features as the creatures come to feed or take a drink. You may be lucky enough to catch sight of mice and other small rodents or even a badger or fox if your garden is accessible to them.
In the autumn months you may be able to see hedgehogs looking for somewhere to hibernate for the winter. If it is possible to site a camera at ground level, there will be a greater chance of seeing wildlife up close.
Being able to monitor the species of bird that are using your bird table is really useful as you can tailor the food you put out to the species for instance mealworms are a favourite of robins. Even if you are not able to justify using a CCTV system solely for this purpose think about devoting one camera for this purpose, you will not regret it.