 He was the author of "Ornithologia Neerlandica, de vogels van Nederland" (1922-1935), with plates by Marinus Adrianus Koekkoek (1873-1944).These plates were later licensed by Harry Witherby for use in "The Handbook of British Birds" (1938-1941).A species of Indonesian gecko, "Lepidodactylus oortii", is named in his honor.