परावाताः शिलाहाराः कदाचिदपि चातकाः |
न पिबन्ति महितोयं व्रतनस्ते भवन्ति किम् ||
- गरुड पुराण
A pigeon eats (survives on ) just the stalks of corn. The chataka bird does never drink water from the ground. It only drinks water directly from the clouds when it rains. The above birds are only following their nature. Can we say they are penancing?
- Garuda purana