Hi Roger it certainly sounds like they have found another food source if nothing has happened in your garden/area to put them off.
Just keep a small amount of food out in case they return so you don't waste any, I would have thought it would be too early and cold to start thinking about nesting.
Thanks Alan ... two days of absenteeism and this morning it seems things are kind of back to normal ... odd though !
Good to hear your birds are back. It does sound, as Alan said, that they had found another food source - maybe somebody put out a lot of stuff which took them a couple of days to eat? Alternatively, when birds disappear from our garden it often means that somebody is out in a neighbours' garden - or somebody's cat is lurking! Hope they remain back.