Back from the UK and the first night I put out the moth trap on 15th / 16th August (they are released again) I was surprised to find that scarce silver Y moths / skogmetallfly (Syngrapha interrogationis) were everywhere and a count yielded 53 moths of this species. My previous highest count was 22 in August 2022, so I wondered how unusual this was. A quick check on our national species reporting database artsobservasjoner.no and it turns out this was the highest number ever recorded in Norway – next highest was 50 in 1997 in southern Norway and then 25 in Namsos, north of here. This is a moorland species and the larvae live on heather, bilberry and bog bilberry (røsslyng, blåbær og blokkebær) although a Swedish page mentions that they can also live on birch; see https://vilkenart.se/Art.aspx?Namn=Syngrapha%20interrogationis
This is a regular visitor in my garden in small numbers and both the high counts were made with the moth trap very close to a large Buddleja davidii in full flower.  I haven’t yet seen them on the Buddleja, but I found at least one picture of this species on Buddleja, see https://www.lepidoptera.no/omrade/?a_id=1018865, so I guess this is what is attracting them as my garden is a few kilometres away from its moorland habitat, unless they have adopted birch in the garden.
At the same time there are less than normal numbers of its cousin silver y (gammafly) and large yellow underwing (hagebåndfly) both of which frequent the Buddleja, sometimes in large numbers! Scarce silver Y is largely a night flyer as is large yellow underwing whereas silver Y flies both night and day!