https://digitalcommons.unl.edu/biosciornithology/87/
"Using molt limits to age Western Bluebirds" by Daizaburo Shizuka and Janis L. Dickinson
Using data on the extent of prebasic molt in known-aged adult and first-winter Western Bluebirds (Sialia mexicana), we assessed the accuracy of the molt limit...
western bluebirdsusinglimitsageshizuka
https://www.westernfrontassociation.com/branches/united-kingdom/leicestershire-rutland/events/2026/february/bluebirds-over-the-white-cliffs-of-dover/
Bluebirds over the White Cliffs of Dover | The Western Front Association
white cliffswestern frontbluebirdsdoverassociation