Do herons migrate?

I have been on the boat quite a bit over the winter and it's been months since I saw a heron. In fact, it was only last week that I saw the first one on the Ouse this year. 

So where have they all been hiding? Do they migrate, move to another river or perhaps the coast, or have they been hunkering down behind the bushes and in the ditches so I can't see them?

To help resolve this issue, the RSPB clearly states the British grey heron doesn't migrate. So, I guess I've either missed them or they've been hiding somewhere.

Then to confuse me, another website says that, while British herons are mostly sedentary, some do migrate to Ireland and the near-continent, such as France and Holland.

To confuse me even further, the site goes on to say, in winter, the northern European Grey Heron arrives in eastern Britain, especially along the coast.

So, there we have it. Some of them are like spotty teenagers and just stay at home, some of them are more adventurous and go to Ireland and the near continent, and some of the international jet-setters fly in from the northern Europe.

I wonder if the one I saw last week was returning from somewhere, having a stop-over while going somewhere else or just hanging out in the Ouse as it always does.

Your guess is as good as mine!