Farne Islands: Possible roseate tern

A pair of roseate terns have been on the Farne Islands all summer, I'm not sure if they have attempted to nest.

Here is a photo (I think) of one of them with an arctic tern behind for comparison.

The key points to note are:

• Overall whitish colour to upper parts
• Tail streamers that extend well beyond wing tips
• Dark edges to outer primaries

The bill and leg colour is clearly different to the arctic tern, but the bill should be black with a possible red base. In this bird the bill appears to be a 'dirty' red colour throughout its length.

I would be interested in anyones comments, currently I have this down as a 'rosy'.