This video is about a robin singing.
From Discover Magazine:
Robins start with a magnetic compass in both eyes, and end up with just one
Here’s an amazing fact: Adult robins have a magnetic compass in their right eye that allows them to sense the direction of the Earth’s magnetic field, and navigate when all other landmarks are obscured. Here’s an even more amazing fact: Baby robins have two such compasses, one in each eye. They lose the left one as they grow up.
Robins kick-started the study of magnetic senses in the first place. In the 1950s, a German biologist called Hans Fromme showed that robins would always try to escape from a cage in the same direction when it came time to migrate. Even though they had no visual bearings, they headed south-west, as if sunny Spain lay just beyond their cages. In 1966, the husband and wife team of Wolfgang and Roswitha Wiltschko showed that a powerful magnet could disrupt this constant vector, sending them skittering in all sorts of directions.
The Wiltschkos have been studying the magnetic sense of robins ever since. In the 1980s and 1990s, they showed that their compass depends on light. They need some of it, and blue-green wavelengths in particular, to find their way. And in 2002, they showed that the compass lies in just one eye – the right one. If they wore a one-sided goggle that blocked their left eye, they could navigate just fine within their featureless cages. If their right eye was blocked, they headed in random directions. It’s not just robins. They right-eye compasses that the Wiltschkos discovered also exist in Australian silvereyes, homing pigeons and domestic chickens.
The story seemed pretty straightforward, but Henrik Mouritsen threw a spanner in the works. In 2010, he showed that garden warblers have compasses in both eyes. A year later, he found that the same was true for both robins and silvereyes.
Now, the Wiltschkos have returned with an answer to Mouritsen’s contradictory results. By studying the same robins over multiple years, they have shown that these birds begin with compasses in both eyes, before settling on just one.