काकः कृष्णः पिकः कृष्णः को भेदः पिककाकयोः ।
वसन्तसमये प्राप्ते काकः काकः पिकः पिकः ॥
The crow is black. The nightingale is also black. Who can tell the differnce between them both? But when it is spring time, it becomes very clear that a crow is a crow and the nightingale is a nightingale.