Just surfing tweeters this afternoon, and I saw a few comments about "why so
noisy?"

Belted Kingfishers are very territorial in both breeding and nonbreeding
seasons, and I have always assumed that whenever they fly, they reannounce
their position so that any potential intruders know to get lost quick. They
call much more frequently in flight than when they're merely perched,
watching for fish.

Dennis Paulson