Definition of "ornithologist"

Mr. Worple in his spare time was what is known as an ornithologist. He had written a book called American Birds, and was writing another, to be called More American Birds.

1919, P. G. Wodehouse, My Man Jeeves

Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus) undergo an irregular, nomadic type of nocturnal migration.

2013 January 1, Paul Bartel, Ashli Moore, “Avian Migration: The Ultimate Red-Eye Flight”, in American Scientist‎, volume 101, number 1, archived from the original on 5 March 2016, pages 47–48