Nature London Chimney Swift Monitoring Program – Report #6 June 2, 2025
Conditions
On June 2, the the skies were mostly clear although several monitors noted the haze in the sky due to smoke from the wildfires in Manitoba and Saskatchewan. The temperature ranged from 17C to 23C depending on the location. There was a light breeze at the outset. It was a pleasant evening with no mosquitoes reported.
Chimney Observations
All 18 chimneys were monitored for this count. The total number of swifts was 604, down from the May 29th count of 738. This decline suggests that the swift migration had reached its peak and will continue to drop for a few weeks. According to Winnie Wake, “In the coming weeks, expect declines in roost numbers as the last of the migrants pass through the city, but London always has several chimneys that host roosts of non-breeders throughout the summer. Only time will tell which chimneys the swifts will choose this year for their summer roosts.” (June 2, 2022)
There continued to be large roosts Hunt (144), Smith Fruit (139) and somewhat smaller roosts at King’s College (96), Huron (95), Elborn (47) and Phoenix (40). All other chimneys held between 2 and 7 swifts.
Observations of Swift Behaviour
Swifts started entering chimneys in small numbers shortly after sunset (8:58 p.m.) with the last ones in almost 30 minutes after sunset. Courtship behaviour was again noted at several chimneys – flying in pairs and a V-formation, swifts flying in threes and fours in tight formation. These behaviours indicate that pairs have formed or are beginning to form, preliminary to mating and nesting.
Glenn and Susan Berry
June 4, 2025
