Painted thread - oil painting

Until XVIII in Europe was a myth in religious and scientific field, that swallows not migrate to hot countries, but live under water. People believed to this nonsense up until 1900. But in middle of the century Johann Leonhard Frisch set up experiment to prove that swallows migrate: he binded painted thread to swallow's leg, and when they came back, thread remained colored: it proved that they didn't hide under water. Unfortunately, I have no idea, on what exact species of swallows he experimented, but I decided to paint common house martin. Bird is migrating in Africa. Painting from imagination. Oil on canvas, 50x60 cm.