Seagulls, magpie and ibis (im not being fun or joking here) have evolved to exhibit cooperative traits and behaviours to get food, including tricking, diverting, cooperating and most annoying literally staunching people.

I was having a burrito on manly wharf a long while back, a seagull just lands on the table and death stares me...i felt uncomfortable and moved, because i know they will try and take my food off me!