But cover, whether natural or artificial, is a double-edged sword. It protects birds but may also shield the approach of a hunting hawk (or a ground predator like a cat). No matter what you do, hawks will continue to kill birds if you attract birds to your yard, because it is natural.
Actual notice. Actual notice is a law term, used most frequently in civil procedure. It is notice (usually to a defendant in a civil proceeding) delivered in such a way as to give legally sufficient assurance that actual knowledge of the matter has been conveyed to the recipient. Personal service, that is, physically handing something to an individual, is usually considered the least-disputable method of giving actual notice.
The law may provide that a public notice put on the courthouse bulletin board is a substitute for actual notice. A prime example is allowing service by publication when a spouse has left the state to avoid service (legal delivery of a legal notice) in a divorce action.