If birds are observed sitting down or starting to huddle, and there is little activity at the feeders and drinkers,
it suggests that birds are cold and corrective action should be taken. First, check that the house pressure is
still correct. If it is, switch off the last fan that came on and continue to observe bird behavior. If bird activity
improves, continue to observe behavior for the next 15-20 minutes to be sure there are no further changes
in behavior.