The book focuses on the ecology of the most important infectious diseases of wild avian hosts, especially those with high morbidity and mortality rates. Disease ecology is an important scientific approach to study the relationships and interactions between living organisms, their environment, and potential pathogens. Birds have high diversity, and the very special ability to fly and migrate. They migrate over long distances, and share ecosystems with other animals, even humans. They serve as the most important natural source of several pathogens with zoonotic potential. Bird-pathogen interactions are increasingly changing due to the continuous anthropogenic disturbances in habitats and ecosystems. With intensified climate change and improved environmental conditions for vectors, as well as higher susceptibility of avian hosts due to simultaneous exposure to environmental stressors (e.g., contamination, food limitation, etc.), the probability of emerging new infections and their expansion into new territories increase tremendously. The Covid-19 pandemic has shown that neglected ecological and epidemiological interactions between wildlife, domestic animals and humans are paramount to global health. The book has a different approach to understanding complex and multiscale interactions among various ecological factors for the most important infectious diseases of wild birds. It provides valuable data to students and everyone who deals with avian species including biologists, researchers, conservationists, and policymakers.