In the avian world, it is the law of the jungle, the survival of the fittest. The larger and stronger bird always bullies the smaller and weaker, especially where food is concerned. There are exceptions of course, where smaller (but not too small) birds can be more aggressive and attack larger but more timid birds.
Also, the mature birds are usually stronger and more experienced than the immature.
This is seen in the image sent in by Lee Tiah Khee, where an adult Brahminy Kite (Haliastur indus), after an exciting aerial chase, successfully grabbed the fresh catch of a juvenile. The juvenile put up a spirited fight but ultimately experience and size got the better of the situation. The adult dominated the struggle, ending up above the juvenile, to successfully wrest the food away from the latter’s talons. So the juvenile lost its hard-earned meal, some of which plummeted to the ground, and hopefully learnt a lesson.
Note that the adult (above) has a distinct white head, neck and breast that contrast with the chestnut belly and underwings. Also, note the obvious signs of moulting primary, secondary and tail feathers.
The juvenile bird (below) shows distinctly pale primary-wing panels, dark secondaries and dark-tipped primaries.
Lee Tiah Khee