I remember many years ago sailing on a round patrol from Lowestoft to the Dutch coast (for afternoon tea) and back. halfway over a flock of racing pigeons decided to take a rest on our flying bridge, when we got a few miles from the Dutch coast, most had flown off towards the Netherlands but a half dozen stayed sheltering, tucked behind the weather guard. from where they were, all they could see was grey walls and some sky, from my station at the chart table, I could see them on the flying bridge as there was a small eye level window which was at deck level where they were. I mentioned this built in compass thing to my commander who said 'OK, let's test this - let's box the compass!' so for the next fifteen minutes or so we slowly described a pirrouette pointing our nose at each compass position, at first, the pigeons got very agitated, but then settled down and just kept shuffling around - always pointing towards the Durch coast. when we finally set sail again for Blighty, one by one, the pigeons took off in the direction of Holland....apart from one which stayed on board all the way back to Lowestoft whe (quite wisely) it decided that to start the long slog back to Holland was the most attractive option