In this case, the most obvious explanation is the fact that they've been breathing in poisonous air (smoke) for weeks on end. Anecdotally, I've heard very littl

In this case, the most obvious explanation is the fact that they've been breathing in poisonous air (smoke) for weeks on end. Anecdotally, I've heard very little bird chirping in the past few weeks while the smoke was at its heaviest, whereas normally the birds are active all day.