How to protect frogspawn from birds

I have a garden pond in which a number of frogs produce spawn every year. However the pond is used by bathing starlings and last year a flock of up to 20 or 30 were so vigorous in daily bathing that they completely destroyed every clump of spawn. None developed into tadpoles so we had no new small frogs last year. Now I know that starlings are in decline and need help but I don't want them to repeat the destruction again this year. I do provide large bowls of water away from the pond for the birds. Obviously I don't want to use any kind of net that can entangle birds and the pond is also used by hedgehogs that visit and sometimes live in my hog boxes. Any ideas on an effective way to protect the spawn from the crazy bathers so the spawn has a chance this year? Amazingly the frogs have already started mating in the pond so it won't be long before protective action is required.