13,000 swallows go into a chimney and hide from view

A bird of prey is waiting for the swallows to arrive.
They rotate as far as they can. The temperature is dropping and the cold is a threat to them.
Giving a sacrifice saves the lives of other swallows.
13,000 swallows go into a chimney and hide from view.
The locals kept the chimney inactive so as not to endanger them.