[2] He was joint leader (with Herbert Lang) of the Lang–Chapin expedition, which made a biological survey of the Belgian Congo between 1909 and 1915.

For his work The Birds of the Belgian Congo, Part I, he was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences in 1932.

Under the cover of special assistant to the US consul based in Léopoldville, Chapin took the code name CRISP and reported back military and economic information.

He was then admitted at a psychiatric clinic, was finally discharged in September 1943 and went back home.

[6] Chapin returned to the Belgian Congo in 1953 to continue fieldwork which he had started more than half a century earlier.