[Grammar] ‘at night’ versus ‘by night’

[northpath]

When should I prefer ‘at night’ and when ‘by night’?
For example:
At night the temperature drops below zero.
Many animals hunt by night.

 

[jutfrank]

• at night emphasises when
• by night emphasises how

 

[GoesStation]

If you think by night may be right, look again very closely. It's much less common than at night.

 

[northpath]

Thank you very much – that’s what I had in my mind but could not formulate. ‘by night’ has a slight negative connotation.
For example: These people come by night and conquer by stealth.