Van Zan and Alex tell Quinn that there is only one male dragon and, like fish, the females lay their eggs and the male makes a "pass" to fertilize them. Yet when Quinn discovers the egg inside the downed dragon, there is an embryo visible, which should only happen AFTER fertilization.
As the occupants of the castle crowd the ramparts to repel Van Zan's approaching column, the men all have their weapons up, ready to fire. If you look over Creedy's shoulder, the man beside him has neglected to flip up the foresight of his SLR, making it impossible to aim the rifle properly.
After leaving Quinn to Join Van Zan's forces, Jared returns and meets Quinn in what's left of the orchard. In the first part of the scene Jared is carrying a Sterling submachine gun slung over his shoulder; you can clearly see the distinctive pistol grip and curved magazine. Towards the end of the scene, as he hugs Quinn, the Sterling has been replaced by an SLR, the British version of the FN rifle. All you can see is the Shoulder stock, but it is unmistakable from its shape. The Sterling only ever had a folding metal stock.
Van Zan mentions that he was able to kill a dragon during "magic hour" -- what was he talking about?
Van Zan was talking about a specific time of day near sunset called "magic hour" or "golden hour", when the light from the sun is softer. Van Zan had deduced that the dragon he killed (and the rest of its species) have impaired vision at that time of day. We see evidence during the final battle with the male dragon in London: while it hunts Quinn, Van Zan & Alex, we see things from it's perspective, which is distorted & somewhat blurred, making it harder for the dragon to see them.