It's not silly or deliberately cruel. Birds do not have a sense of morality or cruelty, those a human concepts. What this parent is doing is brood reduction. It kills the youngest and weakest chick or chicks to help ensure the long term survival of the strongest chicks. Storks do this intentionally and without fail.
TRAGIS_BEGINILAH NASIB ANAK BURUNG YANG MEMPUNYAI IBU TIRI