Not quite the longest evening of the year, but one day away, however it was interesting to compare June 21st this year with the same date in 2019. Both were clear of cloud. In 2019 the second of the swift pair came back to the nest box to roost at 10.21pm. I was keen to see if the swifts could beat this record and come in later. But at exactly the same time, 10.21pm the second arrived back to roost.
It was a beautiful summer evening. The scent of honeysuckle wafted around the garden. I remembered that on the same date last year I had watched a late swift come in and then noticed noctilucent clouds. I decided to stay up late. Sure enough, sometime after 11pm the noctilucent clouds started to show. They only appear at twilight around mid summer. They are incredibly beautiful, being a silvery pale blue in colour. At around 50 miles from the surface of the earth they are the highest known clouds.
The young swifts are growing at an incredible rate. Their first feathers are beginning to show now. The parents come and go in complete silence and often leave the young in the middle of the day.
Below, swift coming in to roost at 10.21pm.
Below. Photograph of noctilucent clouds at 11.45pm, taken in Gilling East.
Below. Swift nestlings now approximately 6 days old.
Jonathan Pomroy 
How interesting that they returned at 1021pm both years. I wonder if other dates would show similar correlations, perhaps giving further insights into exactly what levels of light, or other factors such as time after sunset, cloud and weather, trigger the return?
Reblogged this on Wolf's Birding and Bonsai Blog.