Video: Stork Chick Ejected From Nest by Parents

At first glance, it may appear cruel that this adult stork threw its chick from the nest. But it likely did so to ensure the life of the other four chicks. In a three-year study titled “Motives for Parental Infanticide in White Storks Ciconia ciconia,” researchers observed such behavior in nine out of 63 stork nests. Eight out of nine times, the male killed the chick.

Essentially, the parents do a cost/benefit analysis of the number of chicks in their nest. Four chicks had already hatched successfully, a large brood to begin with. So, when one late-bloomer crashed the party, it became apparent that there wasn’t going to be enough food to go around. The parents could risk all of the chicks starving from stretched resources, or limit the number of mouths to feed.

According to a 2002 study, paternal infanticide is a rare means of decreasing brood size. Most birds just let the siblings sort it out—a baby bird battle royale at every regurgitated feeding until the weakest one succumbs to starvation. But apparently, stork chicks aren’t aggressive enough, so the parents have to do the dirty work themselves.