Birds have clever solution for a cuckoo conundrum
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2014/05/sz_wren_free.jpg?fit=860%2C460&ssl=1)
Female fairy wrens sing to their young while they’re still nestled inside their eggs. The song teaches the babies a password that they can later use to obtain food.
Jon Sullivan/Flickr (CC BY-NC 2.0)