Ornithology is a branch of zoology that concerns the study of birds. Many bird watchers refer to themselves as ornithologists, but the term itself refers to a serious scientific study. The word "ornithology" derives from the ancient Greek ὄρνις ornis ("bird") and λόγος logos ("rationale" or "explanation").

Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. Most marked among these is the extent of studies undertaken by amateurs working within the parameters of strict scientific methodology.

In regard to the other possible answers:

- Numismatics is the study or collection of currency.

- Philately is the study of stamps and postal history and other related item.

- Numerology is the study of numbers.

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