Bird ringing in the context of "Chroicocephalus ridibundus"

Ornithology, from Ancient Greek ὄρνις (órnis), meaning "bird", and λόγος (lógos), meaning "study", is a branch of zoology dedicated to the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. It has also been an area with a large contribution made by amateurs in terms of time, resources, and financial support. Studies on birds have helped develop key concepts in biology including evolution, behaviour and ecology such as the definition of species, the process of speciation, instinct, learning, ecological niches, guilds, insular biogeography, phylogeography, and conservation.

While early ornithology was principally concerned with descriptions and distributions of species, ornithologists today seek answers to very specific questions, often using birds as models to test hypotheses or predictions based on theories. Most modern biological theories apply across life forms, and the number of scientists who identify themselves as "ornithologists" has therefore declined. A wide range of tools and techniques are used in ornithology, both inside the laboratory and out in the field, and innovations are constantly made. Most biologists who recognise themselves as "ornithologists" study specific biology research areas, such as anatomy, physiology, taxonomy (phylogenetics), ecology, or behaviour.

An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular region. Endangered species may be at risk due to factors such as habitat loss, poaching, invasive species, and climate change. The International Union for Conservation of Nature (IUCN) Red List lists the global conservation status of many species, and various other agencies assess the status of species within particular areas. Many nations have laws that protect conservation-reliant species which, for example, forbid hunting or harvesting, restrict land development, or create protected areas. Some endangered species are the target of extensive conservation efforts such as captive breeding and habitat restoration.

Human activity is a significant factor in causing some species to become endangered.

An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular region. Endangered species may be at risk due to factors such as habitat loss, poaching, invasive species, and climate change. The International Union for Conservation of Nature (IUCN) Red List lists the global conservation status of many species, and various other agencies assess the status of species within particular areas. Many nations have laws that protect conservation-reliant species which, for example, forbid hunting or harvesting, restrict land development, or create protected areas. Some endangered species are the target of extensive conservation efforts such as captive breeding and habitat restoration.

Human activity is a significant factor in causing species to become endangered.