Book excerpt: This book assembles, critically analyses and brings forward our current understanding on avian innate immunity and its modulations by different viral immune modulators. Birds are one of the most abundant and diverse classes of living being in the universe, which play fundamental and decisive roles in maintaining ecosystem and biodiversity. Both at the standpoints of anatomy and physiology, avian species are unique organisms with assorted characteristics. Due to these features, avian species are excellent model animals for behavioural and pathological studies. Moreover, some avian species such as chicken, ducks and turkeys are important and economical source of meat, and are kept as poultry species. At one end, these poultry birds are meeting ever-increasing demand of the food security while at the other side these are major concern for public health. This book summarizes our knowledge on responses of avian species to viruses, the molecular mechanisms and comparative functional dynamics in diverse avian species. Avian Innate immunity is special, for instance in interferon (IFN) related pathways significant evolutionary adaptations have been reported in chicken, which make chicken interferon system both structurally and functionally unique. An aspect of chicken IFN system gaining attention is the IFN-induced proteins with tetratricopeptide repeats (IFIT) which regulates the pattern recognition, the JAK-STAT signalling and the protein translation. Despite the fact that chicken responds potently to several viruses, it contains only IFIT5 in contrast to mammals, which have IFIT1, IFIT2, IFIT3 and IFIT5 genes. These are only few examples of chicken genome diversity in IFN pathways and such genetics and functional differences are common not only in chicken but also in other avian species. This book will help you to grasp avian innate immunity and its comparative immunogenetics, which is essential for understanding the evolution of birds in general, as well as the dynamics of avian species in responding to viruses and emerging pathogens.