40,000 bluebirds housed in Idaho, USA
This 25 July 2019 video from the USA says about itself:
The Birdman of Idaho Has Built Homes for Over 40,000 Bluebirds
He just might be the biggest bluebird landlord in Idaho. Al Larson has built and placed more than 350 wooden nest boxes throughout the state’s southwest. The birdwatcher started the project in the late 1970s after reading how important the shelters are to the survival of bluebirds. Today, at the age of 97, he is still at it. Larson monitors the little houses to record vital data about the number of eggs and nestlings. To date, Larson has helped fledge over 40,000 bluebirds.