What made the young seagull finally …

Short answer:

The young seagull was so hungry that he could not resist the temptation of the food. His hunger for food compelled the young seagull to finally fly.

Long answer:

The young seagull had been hungry since last day. He made gestures to be noticed by his parents but nobody cared except his mother. He saw his mother tearing a piece of fish with her beak. He got maddened by the sight of food. Actually, his mother was enticing him. She thought that her son would make an attempt to fly to snatch the food from her mouth. But, contrary to this, the young seagull started begging his mother to bring him some food. His mother took the advantage of the situation. She took a fish and started flying across the sea towards her son. She could see her son screaming with joy. As soon as she reached near him, she stopped and didn't pass on the food to him. Her son stood surprised for a moment but he made the dive unconsciously to have the piece of fish.
The young seagull was so hungry that he could not resist the temptation of the food. His hunger for food compelled the young seagull to finally fly.