Hahaha. Fuck me. Where to start.
The water acts as a barrier for ionising rays, i.e it'll prevent you being irradiated with a lethal dose as would happen if you were stood near the spent fuel and the pool was empty. It also cools the spent fuel and prevents it melting and releasing huge amounts of extremely radioactive gases.
But most of the fuel in that pool is decades old, it's neglected and some of it has literally eroded into highly radioactive sludge and sediment.
The pool is full of that stuff.
Those birds in the pool will pick up particles of very dangerous radioactive substances on their feathers, and then they'll carry it to wherever they leave to.
Like
@andyhinch said, some of the birds that roost and nest on the site, and congregate there, are so radioactively contaminated that when they leave the site they pose a threat to the health of people who come into contact with them. There are people in Seascale that have literally had their gardens dug up because they've been so contaminated by such birds that their garden exceeded a threshold to qualify as radioactive waste.
The spent fuel pool in question is an embarrassment to the industry and is utterly shocking to anyone with a clue. It's genuinely infamous, as much as the state it's in has been attempted to be covered up for so long. It's one of the worst examples of neglect in the industry in Europe, it's an embarrassment for the government and Britain. It's going to cost the taxpayer billions to clean up as part of the decommissioning of the site and others like it.
If you don't find those images shocking then I'm afraid you're staggeringly short of a clue. A rudimentary understanding of this topic would be a step up for you fella.
You just seem determined to dismiss this as an issue, even pointing to pedantry about the family of birds mentioned in the BBC link earlier. Laughable.
Genuinely one of the funniest things I've read in a while. You're deluded mate.