I use black, heavy duty (but light and flexible), anti-bird net from http://www.lbsbuyersguide.co.uk and it lasts for many years. However pigeons can peck through it so support is needed. A simpler method is to cover beds with enviromesh, standard grade, no supports needed as plants can push it up, just a few weights along the side, not buried, so it is easy to remove for weeding. Rain passes through, most insects do not and birds cannot do any damage.