You have to pick:

I suppose I'd probably just have the shampoo bottle "amputated" and get a regular prosthetic. Sucks to lose a leg though.

After quite a bit of Googling I'm pretty sure that there's no such species of gull, so I'll assume some sort of average gull for purposes of argument. The smallest gull is the 120 gram "Little Gull" and the largest is the 1.75 kg Great Black-backed Gull, so I'll say the average gull is 935 grams. An adult human large intestine can normally hold a maximum of just under 4 liters without danger (Google found _that_ information pretty easily for some reason). So, assuming seagulls have a density comparable to water, that's four seagulls one can fit safely inside a human large intestine. Five would be pushing it. Once the seagulls are in there it's probably only going to be a matter of seconds before they all die. They've got sharp beaks but I doubt they'll have the room to peck, so I wouldn't worry too much about their struggles. Emergency surgery to remove their corpses will still be needed stat, though - even if they weren't tied in place I doubt it would be possible to pass them normally. This is going to be a super embarrassing scenario, with the risk of fatality increasing dramatically if a "flock" numbers more than five.

I think the intent is that the seagulls are outside but are tied inside of you via string. Although your interpretation is perhaps more interesting.

that would really suck to have to have a flock of any kind of sea gull tied to your insides.
What if they tried to fly away and started ripping your insides

Bryan...You're brilliant.

Can I keep things other than shampoo in it? Like, booze? Always the life of the party then. Pants would suck though.