Hypothesize how birds being endotherms or warm blooded can be an advantage to them.?

Answer 1

Creatures that are not highly endothermic usually need to adapt in other ways. They either try to restrain themselves to environments that support whatever range they're comfortable in or they have very complicated metabolisms and correspondingly uncomplicated organ systems. You can see how either of those could be a massive limitation to a bird.

Though birds that fly have a huge mobility advantage, there is also a lot of temperature variation with altitude. Birds that must stay warm couldn't fly high (negating much of the advantage of flight in the first place) and those that had to stay cold couldn't land in most places (an obviously unworkable solution).

Having the ability to maintain a constant temperature allows a metabolism that can be geared up to very high and very low levels (otherwise chemical reactions dependant on temperature would have trouble). This allows both the high energy output needed for flight, but also the low energy output when just picking worms out of the ground.

For something that doesn't move much or that lives in a fairly constant environment, endothermy may be of no concern. But I doubt the most birds could survive without it!