Dragon gestation..

[Shinobody]

How about improper conditions (not lava-like temperature, too short time of hatching or smth) resulting in birth of a Drake?
Then that throwaway line about Drakes being "actually a dragons" we can see in "Secret Lore" wiki page would make some sense...
Also, isn't gestation referring to creatures which give live birth rather than hatching from egg? English is not my first language, but...
As for canons in Wesnoth: yes, there aren't many. The point is, there should be one, but there are few. B4W is basically giant fan-fiction to some others fan-fics universe.
Also: Why someone should hunt a dragon? Dunno, I think armorsmiths would pay handsomely for dragon's scale, material unseen for centuries, and magi would kill for chance to dissect them.
Screw sleeping on pile of gold, dragon's body is pile of gold.

[Boldek]

But why fight a enormous beast if you can just slip in while it naps and loot the place?

[Shinobody]

But why fight a enormous beast if you can just slip in while it naps and loot the place?

Also: Why someone should hunt a dragon? Dunno, I think armorsmiths would pay handsomely for dragon's scale, material unseen for centuries, and magi would kill for chance to dissect them.
Screw sleeping on pile of gold, dragon's body is pile of gold.

Dude! Where are my scales?! And kidneys? Damn, I'm never gonna do any business with mobsters anymore!

Also: Fame of a dragonkiller (also known as fudgeton* of XP).
Also: Have you read Hobbit? Dragons don't take stealing from them lightly. Cities get burned and stuff. (And Smaug wasn't even sure, but just wanted to be on the safe side.)
*- no, it's not a real swearword.

[Boldek]

True. But like in Beowulf, people seem pretty ready to take their chances. No, maybe that dragon was gone or something, I don't remember the details.