If memory serves me right, I have so far visited Skomer on six occasions, once as a day trip some time in the 1990s (no bird pictures) and a further three one-day visits, on 17 July 2018, 5 July 2022 and 11 July 2023 (with bird pictures). Also stayed on the island on two occasions, once between the 11th and the 13th of May 2017 and a second time between 30 April and 2 May 2024. The Walking Notes and the Birds List both refer to the latter five.
For reference, a few websites from the Wildlife Trust of South & West Wales:
See also entry on birdingplaces.eu.
Marnix's Bird Gallery 