The set of creatures affected by Dawnfeather Eagle’s triggered ability is determined as the ability resolves. Creatures you begin to control later in the turn and permanents you control that become creatures later in the turn won’t get +1/+1 or gain vigilance.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.