Did you know that birds sing to their eggs before they hatch? It sounds like a Disney movie, but it's true, and the song may actually affect the babies' growth. Two groups of eggs were placed in an incubator to two different type of chirps, and those eggs who received the chirps of birds during a hotter temperature grew smaller than birds who heard regular birds singing. The story sounds slightly unbelievable, but birds can control the size of their offspring.

Source: http://phys.org/news/2016-08-baby-hot-birds-eggs.html

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