The 'Strange Duck' is a Snow Goose?

This afternoon I also got some photos of the 'strange duck' that Zoe and I first saw a couple of weeks ago.  I now reckon that this bird is a blue-phase snow goose [However, see update below].  The snow goose (Anser caerulescens) comes in two colour phases: the more common white phase which is mainly white but with black wing-tips, and the blue phase which is mainly black but with a white head.  The illustrations in BWP-CE and photos on the web do not give any indication of the beautiful scale-pattern in black and dark green that was visible on the back of our bird.  In some lights the dark green turned to a dark blue  (presumably this is where the term 'blue phase' comes from).  Here is one of the photos I took today:

Again, this bird was fairly persistent in begging for food: it got out of the water when Zoe rustled an empty carrier bag, which none of the other birds did, and I reckon Zoe could have had it eating out of her hand if only she had had some bread left.  This familiarity with human beings suggests an escaped captive bird rather than a vagrant that has wandered in from North America or Siberia.

Update on Thu 2005-01-13 by Tristram Brelstaff

Liz and Zoe report that someone they talked to today says this bird is actually a muscovy duck (Cairina moschata).  Muscovy ducks are natives of South and Central America but they have been domesticated and are now found all over the world.  Their plumage tends to be very variable.