Silence

आत्मनो मुखदोषेण बध्यन्ते शुकसारिकाः |
बकास्तत्र न बध्यन्ते मौनं सर्वार्थसाधनम् || – सुभाषितरत्नसमुच्चय
Meaning : Parrots and other talking birds get captured due to their own folly. Storks are not captured. Silence is instrumental in attaining all purposes.