in 1899, mary day of new jersey observed a pair of chimney swifts nesting in a chimney, and noted the incubation period was 19 days. the first detailed study of chimney swifts began in 1915 by self-taught ornithologist althea sherman in iowa. she commissioned a 28 foot tall tower, of a similar design to a chimney, with ladders and peep holes installed to facilitate observation. chimney swifts nested in her tower, and for over fifteen years, she meticulously recorded her observations, filling over 400 pages. sherman remarked that although the tower had been designed with a limited knowledge of the nesting behaviour of chimney swifts, after many years of observation she believed that the original design was ideal.