Grey Herons (and Rooks) (19 April 2003)

For those of you who haven't enjoyed the delights of Grey Heron Ardea cinerea ringing, and all those who have but want to be reminded of it, this posting shows a few photos from this season's efforts, the sixteenth year of MRG's intensive heron-ringing study.

At the Budworth (Marbury) Mere heronry - last year the biggest in the country with 150 occupied nests - some chicks had, as usual, fledged from the earliest nests. Some must start nesting at Christmas! Most of the chicks were pretty big, weighing ~1.5kg each, and had legs and heads almost fully grown. All chicks were weighed and measured as well.


Almost all Grey Herons in Britain are ringed as chicks, and most of the ringed birds that are found are juveniles in their first year of dispersal. There is, therefore, little information on recruitment to the breeding colonies and natal fidelity or otherwise. To try to remedy this, for several years in the mid-1990s we put colour-rings on Grey Heron chicks, as well as the metal ring, hoping to be able to see them on adult birds in or near the colonies in future years. In fact, despite our watching several hundred birds, very few ringed birds were seen and no significant information gained. The origins of the breeding adults remain a mystery. Some of the colour-ringed birds must still be alive; if you see one, anywhere, please note the colours and the two letters on the ring, and report it to

As an afterthought, one of the complaints sometimes made about ringing is that the birds that we usually concentrate on don't represent much of the total avian biomass and hence impact on the countryside. Much of the total is made up of pigeons, pheasants, corvids and so on. The birds in the Marbury heronry, with approximately 150 pairs of Grey Herons and an average of two chicks each, weigh about 1 tonne in total.

After spending enough time in the heronry, we went to a rookery. As we expected following all the dry weather, the adults were obviously having difficulty finding worms and most nests had only one chick (from four eggs laid) although one nest had two. We ringed 11 Rook Corvus frugilegus chicks, the first for MRG since 1996.


David Norman.


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