Ornithologist is a type of zoologist who specializes in the study of birds. They study the evolution, behaviour, genetics, life processes, migration patterns, and habitats of birds. Ornithologists may work with wild birds, or birds in zoos or sanctuaries. This field of science has a long history dating back to the Stone Age. The ancient Greek polymath Aristotle mentioned about bird migration, egg laying and moulting in 350 BC. Bird watching began evolving from the early 19th century with the invention of the telescope. With development in technology, a variety of sophisticated and modern tools and techniques are used today to study birds. Ornithologists work in the fields observing birds and collecting samples such as eggs, nests, bones, etc. These samples are them analyzed in the laboratories and results are published in scientific papers. Research on birds helps to classify and understand the various species of birds, and provides information on the effects of climate change, pollution and human encroachment on the lives of different types of birds. Ornithologists may work in research institutions, governmental agencies, zoos and sanctuaries, and environmental agencies. Read on to browse through a list of world famous ornithologists and read their biographies and timelines.