The Chimney Swift is a common statewide breeder. Although always a notable presence historically, this species has increased considerably in the CW Region due to the abundance of open-topped chimneys that mimic the structure of hollow trees - the swift's most frequent natural nesting place. BCN eBird trends may not accurately represent the population at large which is mostly centered around urban areas that are not frequently monitored. BBS trends indicate that this species is decreasing significantly in both IL and the upper Midwest and populations here may decline dramatically as modern chimneys continue to be capped off at greater rates.