If I'd been in the audience, I'd have asked Eric about cargo ships instead of trawlers. And ferries. And container ships. And..
Them seagulls (as Eric calls 'em) follow all of 'em. Are they really all hoping for scraps? Well, some at the RSPB think so:
But I'm not so sure. Several years back there was an interesting thread on this on Essex birders, and the Thames seagullers chucked some tasty ideas into the froth.
Feeding? Well, the feeding rates are extremely low. Little is thrown overboard, Relatively little churned up in the wake.
Migration? See that following paragraph in the quote above; over-simplified, small scale adjustments don't rely on those large-scale aids.
Competition? Some seagulls drop back and follow the next boat as well. And the next. Somehow utilising for display.
Play? Nothing better to do? Well, most seagulls would normally just loaf and save energy. And you don't really see seagulls play- normally too busy squabbling. Pair-forming perhaps?
Seagulls have to work hard to find food, happy to be opportunist feeders, and aren't really pelagic. They're not sea-going gulls. More inshore water gulls.
So, when a flippin big moveable cliff motors through your large feeding territory, creating easy lift to gain a bit of height to look further for seagulls feeding elsewhere, extra lift to allow some lazy flight, a hitched ride for several miles in the general migratory direction, the odd bit of propeller-prepared chum for a snack, why wouldn't some of the population an opportunist species take advantage?
- Height- watch birds ride the airwaves above the boat, scanning.
- Lazy flight- watch birds ride the bows.
- Migration- at the right time of the year, watch those Kittiwakes follow 'inland' then continue overland when the rivers narrow.
- Food- watch a few dip-feeding at the stern.
- Pairing- watch a group of Mediterranean Gulls in the spring, they are seemingly playing 'King of the Castle', continually trying to out-climb each other.
Kittiwakes. Read the short comments in the guide books. 'Winter far out to sea'. So, a Kitt coming into the Medway must be up to something. Watching for feeding? Not often. Riding the airwaves? Hardly any flapping going on. Deciding they've strayed a bit too far from home? Yup, they soon desert that cargo ship when it enters the narrow channel of the Swale. These birds are more often found in poorer weather than good, but calmer days just after blows are good days to watch out for them. A few tired individuals, having a bit of a laze? Kitts after ships? They're getting tired out over the deeper water. Money is on a few more birds inshore around the Kent coast over the next few days.
The more you find out, the more there is to know.