Breeds every summer, but winter survival rare. Several generations, most frequest May - Sept.
Can turn up in thousands under the right conditions, especially at coastal migration watch-points.
Recent research shows the Silver-Y flies at altitudes of up to 1.2km when migrating!
Recorded in 69 (100%) of 69 10k Squares.
First Recorded in 1834.
Last Recorded in 2019.