Dead Seagulls

Go to the farthest left corner of the beach with a sniper rifle. You will then see some seagulls. Snipe one of them until you think its close enough above you. Like other birds in Halo they just disinigrate in the air, but not these! wait a while and the dead seagull will drift slowly with the current towards you and onto the beach. And when you shoot it blood flies everywhere.