3) Switzerland. There is a feral population in northern Switzerland along the border with Germany that numbers around 450 birds. These gather to moult in July on Klingau Reservoir in northern Switzerland. Counts indicate that these birds are present and flightless at precisely the same time as the Dutch birds (see below) so the two populations are separate. However, even the situation in Switzerland may not be as clear-cut as originally thought. This is because Italian birders have noticed an increase in Ruddy Shelduck records in northern Italy (Po Delta etc) immediately before and after the Swiss moult and they think it possible that the Swiss moulting birds may now include wild Ruddy Shelducks from the small Balkan population.
Records in Britain are no doubt a mixture of escapes from captivity and birds that have either overshot Holland on their way to moult, or birds dispersing from Holland after moulting. This largely explains the July/August peak in Britain. Small parties on the East Coast are of course more likely to involve these Dutch birds. There are no feral populations in Britain although the odd pair has bred from time-to-time but they have never become established.
In 1892 and in 1994 there was a large influx of wild Ruddy Shelducks across northern Europe, with the largest numbers in Finland, Sweden, Norway and Denmark. I can't remember the exact total for 1994 off hand but I think it was around 350 birds. The records strongly indicated an origin in SE Europe/SW Asia, thought to have been provoked by desiccation on their breeding and/or moulting grounds. The BOURC would not accept that any wild birds occurred in Britain in 1994, despite good evidence to the contrary.