This is "Allegory of Virtue and Riches" painted in the Dutch south by Godfried Schalcken. Clearly, in the real world, this couldn't happen: the bird would be much the lighter than the jewellery. But this picture does not seek to depict the real world – it’s an allegorical painting.
The sparrow is probably intended to represent virtue and true love, and the moral here is that no amount of gold and pearls can match the value of the woman's virtue. Her tears suggest that she has traded her virginity for jewels and expensive clothes, and now regrets her decision. The artist invites us to decode the message behind this central image.
The painting itself has jewel-like qualities - it's tiny, painted on a copper plate, which allowed Schalcken to create an exceptionally fine, bright finish. This style of highly meticulous small-scale painting was a speciality of his.
Allegory of Virtue and Riches hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.