Thanks Pete - I have been in touch with John earlier today and he said that had often wondered about gritting behaviour and that they very rarely come to the grit trays after early December so all he could conclude is that the grit they take on in autumn/early winter lasts them right through the winter. But he wasn't sure.
He also said that no one has studied weight increase but there is a German study where they found in 12 stomachs in autumn an average of 609 stones (range 420-830). In spring of 4 stomachs average of only 38 stones. The stones must have been very small. So perhaps they take on grit early in the winter to last them right through the year.
Unless someone has a better theory/knowledge that will have to do for now.
Hello Sid, there's a chap called John Wilson on the Lancaster DBWS site that actually does the ringing at Leighton - I guess he'd either know some of the answers or know someone who would! I reported some ringed Beardies to him and I got some good info back. He might be worth a try? Peter
Several of us have had really good views of the Leighton Moss Bearded Tits on the grit trays this autumn.
I realise that Bearded Tits need the grit in autumn because they are changing from the soft insect diet of summer to the harder, mainly reed seed diet of winter, and that the grit sits in their gizzards and helps grind up the seeds. I also realise that fairly soon now they will stop visiting the grit trays - but why do the stop taking the grit from the trays (presumably they continue to eat seeds during the winter), will the initial grit supply last the winter, do they take grit from the paths as they did before the advent of the trays and finally is anyone aware of studies that show how much (in weight) of grit do they take, has it been possible to determine this????
Anyone looked at this aspect of birding and know the answers?
