NLRG was formed in 1957 to help in the study of birds in the Lancaster and District Birdwatching Society area. There are currently 12 active ringers. Species currently being studied include: Pied Flycatcher, Bearded Tit, Sand Martin, Twite, Goosander, Oystercatcher and Grey Wagtail. Migration has been studied for 28 years at Heysham. We welcome anyone who wants to observe, help or perhaps wish to become a ringer. Photo: A Heysham-ringed Twite on the Mull of Kintyre (thanks to Eddie Maguire)

Friday, 20 November 2009

True Grit (2)

Bearded Tits continue to use the grit trays at Leighton Moss despite the wind and rain. To date we have logged 275 sightings of 75 colour ringed birds. Thanks especially to Keith Kellet and Alan Gallagher and several other birders for colour ring sightings.

This year the birds have followed the pattern of previous years- adults coming in first from early October to be replaced by birds of the year from late October/ early November on.Two birds have been recorded coming back for the past four years. It is too early to analyse this years sightings but our results from 2006 when we had 331 sightings of 97 different birds may be of interest. Of the 97 birds identified 55 birds were sighted on just one or two days but some visited much more often with one bird being recorded on 15 days. Of course we missed many sightings as coverage was incomplete. Close observation suggests that they are to sorting through the fine sand for the right sized particles. They can stay on the trays for up to 15 minutes. There is a very marked tendency for birds to keep together in a flock often visiting the table two or three times a morning as a group and returning with the same group days later.

A German study of 12 Bearded Tit gizzards found an average of 608 (range 470- 830) stones in the gizzards in autumn. No wonder they need to visit the trays often! They need grit at this time of year to help grind up the hard seed of the winter diet of reed seeds.

I have been asked by several birders if the taking on of grit increases the weight of the bird. We have lots of weight data but it would take a lot of effort to analyse it. However what we have done so far shows an increase of ca 0.7 grams from September to December, Bearded Tits average ca 14.5 grams. Of course other factors may be responsible for this weight increase.

John Wilson

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