Why do birds sing as dawn breaks? Indeed, why do some sing at dusk? And for what reasons do they eventually stop?

Eva Sanz, Tarragona, Spain

I am a tenor/countertenor singer with a normal range from G (first line, bass clef) to two Ds above middle C. When I had a sore throat for a few days I lost my upper notes but could easily sing great C, which is two octaves below middle C. Why does this happen? And why do I not retain these bass notes when my throat heals? I always wanted to be a basso profundo.

Len Yaeger, Minneapolis, Minnesota, US

I was sitting outside today and couldn't help overhearing two species of birds singing back to each other. I could tell that they were different species (one was a Tui) but they seemed like they were having a loud conversation across my yard.

It got me thinking... Is a certain animal species able to speak/sing to other species of animals which aren't the same as it?

Does anyone have an answer to end my wondering?

Thanks

Liam :)