I found a very interesting article in LiveScience.com, reporting on a study conducted on hens at England’s University of Bristol. It seems the mother hens reacted in a rather extreme way if they felt their chicks were in distress.
It is believed the hens are showing empathy. The hens were separated from the chicks during the experiments but were in close proximity. When puffs of air were directed at the chicks, the hens “responded more intensely with a stress response equivalent to fight-or-flight behavior,” according to the article.