The Illinois Ornithological Society (IOS) is the principal birding and bird conservation organization in the American state of Illinois.
It produces a quarterly magazine, Meadowlark, A Journal of Illinois Birds.
[1] A website is also available and features updates on rare bird sightings in the state as well as profiles of local birders and links to upcoming field trips.
The IOS has a standing committee (the Illinois Ornithological Records Committee), founded in 1985, which evaluates the evidence for records of birds that are rare or unusual in the state, and which is responsible for publishing and maintaining the official checklist of Illinois birds.
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