On Mon, 29 Nov 2010 08:38:10 -0000, Mike wrote:

This appeared overnight in one of the bird baths.

http://www.myalbum.com/Album-TEKWQV3...-of-Other.html

Odd? :-)

Rare but not odd. Think they need very still conditions to form. The
water forms an incomplete skin of ice but continues to freeze into
the body. As it freezes it expands and forces water out of the hole,
which then freezes. More freezing in the body pushes more water out
the hole pushing the previously frozen bit away from the hole. Looks
like that hole was getting smaller as the process carried on as shown
by the taper in the extruded ice plug.

--
Cheers
Dave.