What is this bird? It is in my garden,

It looks like a sea bird - possibly a young Herring Gull. Advice here is to leave them well alone if they are downed in the garden and are not going to be prey to dogs or in danger. Their parents usually know where they are and will come down to feed them - a bowl of water is appreciated. There are very few rescues that will take them - I do know of one down in Devon. The problem is if they become habituated to humans they can become a nuisance and those beaks can inflict some damage

It was a skua, the rspb have collected it

It’s an adult great skua, I think — not a garden bird at all, so possibly a victim of something like avian flu. Where in the UK are you?