>Are you asking about physics ???
Though related to physics, it's a question posed in Monty Python's Search for the Holy Grail (is that the official title?), a movie from quite a few years ago. I apologize if you already knew that, Enigma, but I haven't any clue as to how popular kooky English humor is in Thailand
>What about a laden swallow?
That's an unanswerable question, so long as we're not told just what it's laden *with.*
>Have you taken into consideration the drag due to air resistance?
Yes, in fact. Due to its small size, the drag coefficient of the bird can be calculated with some simple scaling. That is, it's just two-thirds the power of mass.