Avian influenza (AI) viruses have been routinely isolated from a wide diversity of free-living avian species, representing numerous taxonomic orders. Birds in orders Anseriformes and Charadriiformes are considered the natural reservoirs for all AI viruses; it is from these orders that AI viruses have been most frequently isolated. Since first recognized in the late 1800s, AI viruses have been an important cause of disease in poultry and, occasionally, in non-gallinaceous birds and mammals. While AI viruses tend to be of low pathogenicity (LP) in wild birds, the 2014–2015 incursion of highly pathogenic avian influenza (HPAI) clade 18.104.22.168 H5Nx viruses into North America and the recent circulation of HPAI H5 viruses in European wild birds highlight the need for targeted, thorough, and continuous surveillance programs in the wild bird reservoir. Such programs are crucial to understanding the potential risk for the incursion of AI into human and domestic animal populations. The aim of this chapter is to provide general concepts and guidelines for the planning and implementation of surveillance plans for AI viruses in wild birds.