To be perfectly honest, if you had just posted a picture I would never have thought you looked like a pidgeon, but now that you've said it and then posted a picture, I can kind of see what they mean, but obviously, you wouldn't actually be mistaken for a pidgeon or anything. And you're not bad looking, the way you posted I thought, "Oh god...", but seriously you look fine.
What I mean is that people are always 'alikened' to animals, well maybe I just go to a weird school but people always have random crap conversations like: if (whoever) was an animal what do you reckon they'd be?
But they're obviously not doing that, they're just being crass and quite rude really to laugh in your face. If they don't come and apologise soon (give them a chance to), the next time you see them say: "Looking like a pigeon is better than looking like a dog" or something to that effect. Or, "Well, if I'm a pidgeon I'm certainly more of a bird than you are, look at the jaw on you, bloody hell, you are all complete men" and then walk on.
Like I say, you're not even bad looking so they are just being silly, not so subtly.
PS. I think if you grew your hair out you'd look less like a pigeon, if you are really worried about it (don't be). But extra hair would definitely help I reckon.