So sorry to hear about your frog loss this year. I've seen seven of my eight goldfish, but no body, so the other might still be around. Yesterday (12th. Feb) I saw a bit of movement on the pond and there were two frogs, but no frogspawn. It's really early but my blackbird was also building her nest yesterday.
I was badly frozen up, but I used my invention again of pieces of pipe from an old vacuum cleaner, with the ends tied inside plantpots (to stop snow blocking the holes.) This leaves escape holes for any bad gas to escape. My pond's only about 22inches at the deepest point. Maybe I should patent my invention and make a mint!!