Ornithology is the branch of zoology that deals with the study of birds. Ornithologists research and look at every facet of a bird's life. Some study how birds interact and live in their environment, while others look at how the the bird is structured, and how systems function.
Birds were most likely a vital source of food for humans in early ages. Nearly 80 species remains have been uncovered in excavations from early towns and villages. Poultry and falconry (an art or sport which involves the use of trained raptors to hunt or pursue game for humans) were early hunting techniques used to catch birds a source of food. John Ray (1627-1705) and Francis Willughby (1635-1672) developed the first professional scale system of bird classification in the 17th century. The system used function and morphology, which are more scientifically sound methods, as opposed to behavior, in which information was gathered more from observations, making it less accurate. Ornithology's birth is considered to be a work by Francis Willughby called Ornithologia libri tres (1676), which was also worked on and completed by John Ray.
Ornithology emerged as a specialized science as the idea and learning of natural history, as well as the collection of natural objects like as skins, feathers, and bird eggs became more practiced and common. The sudden spurt in ornithology was also result of colonization. As more and more people began to settle in towns, interest in birds grew, leading to more and more men and women beginning to practice ornithology. The British Ornithologists' Union was formed in Britain in 1858 and published a journal, The Ibis. This union supports the studying and research of birds across the world. Their journal is still being published today. It was in the Victorian era that bird collectors first began to observed many of the variations in bird forms and habits across different parts of the earth. They noted that variations in species were widespread in accordance with their respective habitats. As interest grew, more and more people began to find new species and record them. They sent many of these to museums or scientific organizations. Over time these collections of birds were put into museums and the naming of species with binomials and arrangement of birds into groups based on their similarities in traits and features were the main job for museum specialists. The variations in birds across different regions resulted in the introduction of trinomial names. The Galapagos finches played a huge role in the development of Charles Darwin's theory of evolution. The study of birds and their habitats was notably propelled in Germany. Ornithology can be traced back to as early as 1903. Even with the rising popularity of studying the anatomy; traits and variations of birds, and the distribution of species, people began to gain interest on the study of bird's life-cycles, from reproduction to migration patterns. Bird ringing stations were in Germany as far back as 1903. Bird ringing is a method of studying wild birds that is still used today. This is done by attaching a small ring with a number on the band to the bird's legs or wings. This allows one to study various aspects of the bird's life, as one can re-capture the same bird later. In the United States, ornithology was limited to the study of variations, species, and geographic habitats, it expanded into the study of a bird's life with the influence of Ernst Mayr. David Lack began work on population ecology, though it was rejected by many. People preferred the older and more familiar methods of ornithology. Lack found that population was mostly determined by density-dependent controls. His conclusion, however, was based on the ideal of group selection. Group selection is the idea that alleles can become fixed or spread in a population because of the benefits they give to groups, regardless of the shape of individuals within that group. Group selection was a facet in evolutionary biology until it was studied more closely, and there was skepticism on group selection as a major mechanism of evolution. Lack also introduced the use of many new tools for research. One of his greatest innovations was the use radar to study bird migration. Molecular biology and the growth of genetics led to the new gene-centered view of evolution. This view was basically that of natural selection. Genes competed against one another for survival. As a result, the observations on behaviour, lifestyle, and traits were looked at and studied differently. Thanks to the introduction of new tools used in molecular-biology, new approaches to the study of birds came about. The use of the structure of molecules to gain information on an organism's relationships (molecular phylogenetics) was used to study relationships of birds far more accurately and easily than the the older methods. The older methods relied on human observations and sometimes inaccurate conclusions. Biodiversity also soon became an area of great interest. Biodiversity is the diversity of life within a ecosystem or biome. This research in biodiversity led to the development of landscape ecology. 
One of the main reasons for ornithology's popularity spurt, was the realization that amateurs had chance to contribute to professional biology. These amateurs could essentially give scientists the data that was needed to help fix some central areas of concern in biology. An important and popular new tool became available for ornithology. Field guides were a major advancement. They allowed for easy and quick identification of species and contained other helpful information. The first versions of new generation of field guides were put together by Florence Merriam. Yet another result of the growth of ornithology was the establishment of organizations. Two notable organization are the Audubon Society in the US, and the Royal Society for the Protection of Birds (RSPB), which is located in Britain. The RSPB was founded by women and did not permit men to be members. This was an act of revenge on a policy of the British Ornithologists' Union to disclude women. The organization now allows men as members. As these organizations grew in size and number, many projects were undertaken. Atlases which show in great detail the distribution of different bird species across the country, and "Breeding Bird Surveys" provide information on breeding density of birds and the variations in density through time. There a number of organizations and volunteer projects that can be found all over the world.
Methods and techniques
There are many tools that can be used in ornithology, and new tools are readily becoming available. An early technique of studying was to collect eggs, but since amateurs collected most of these, it is an unreliable method. One of the most prominent techniques for ornithology has been the collection and use of bird skins for documenting different species. Hunters and sportsmen learned how to skin, and as they shot down birds, they sent the sins to museums. This led to mass gathering of skins and of huge collections in Museums. These skins were very useful in that they are used to identify species and compare them as well. Ornithologists used these skins sent in by sportsmen to document and classify species from all over the world without having to do it themselves. Morphometrics uses methods of extracting measurements from shapes. This became very important in in bird systematics. The development of molecular techniques have made it possible to find and classify the species of rare and ancient discoveries. This is done mainly by extracting DNA samples. As for the conservation of bird specimens, Freeze drying has been tried more recently. This technique preserves stomach contents and rest of anatomy of the bird. The problem with freeze drying is that shrinkage can occur which skews the anatomy. The study of birds in the field relies upon one main method, digital photography. Researched can now see and document minute differences in a bird's anatomical structure with ease. Though this is a valuable technique, birds must be captured in order to conduct important studies on life cycles and history. There are several methods for catching birds, bird ringing, as mentioned before, is done after the birds are captured. Mist nets are made up of two poles with the net lined between them. A permit is required to use a mist net. Cannon nets are nets that are triggered and pulled rapidly by explosively-driven projectiles to capture any birds quickly enough before they can escape. Statistics are used to estimate bird diversity and population density. There are several studies in bird behavior, including those on instincts and intelligence. 
Other uses and applications
Birds are often times seen as pests. Bird strikes are one example of birds as pests. Bird strikes occur when a bird strikes a plane, sometimes getting caught in an engine or propeller. It is estimated that bird strikes cost US aviation $600,000,000 annually and have caused 195 deaths since 1988. Humans have played a huge role in the extinction of animals, and birds are no exception. There are many bird conservation societies found all over the world.  Birds are also often kept as pets.
- The Feather Atlas U.S. Fish and Wildlife Service Forensics Lab. High-resolution scans of flight feathers of major groups of North American birds as an aid to species identification.