It'd be interesting if they did think of them as predators. The main penguin-eating things are seals and killer whales, and the thought of a flying killer whale is not something I can sustain for very long. Mind you, I doubt they could sustain it very long - cue either Monty Python's sheep ("Note that they do not so much fly, as plummet"), or HHGTTG ("Ooh, that looks awfully big. I think I'll call it 'ground'. It seems to be coming towards me quite fast. I wonder if it'll be friends with me?").

Grab.