1 min continuous chirping

There’s something about rain that brings out the chirp in sparrows. I counted 12 of them, but the sound of this lot in the ivy and elder bushes sounds like a lot more. Why do sparrows all get up a chirp when it rains?

recorded from Maplin electret inserts on tree at 44.1kHz PCM  to a PC via mic preamp. High-pass filtered from 440Hz at 12dB/octave to reduce traffic noise