This year has turned out to be a record year for the Leighton population of bearded tits. We have ringed 165 juveniles by early September compared with a previous record high of 158 in 1997. At Leighton the first brood which flies in late April is always the most successful, and this year was no exception. The second and third broods are much smaller but this year they have done the best yet and so far we have ringed 35 from the 3rd brood compared with a previous record of 24 in 1995, and there are probably several yet to ring.

Other reedbed birds have also had an excellent season we have ringed 604-reed warbler compared with 403 in 1998 and 324 sedge warblers against 147, with roughly similar effort. However blue tits, which usually enter the reedbeds in late summer and autumn, have been very few with only 50 ringed compared with 179 last year. It has been a good year for reed aphids and some sedge warblers have obviously been feeding up and putting on weight, prior to their departure for Africa. In early September we caught one which weighed 20.6 grams, the normal weight is only ca 10 grams!

The new design of nest box  (or wigwam) has worked well. This onion shaped box without the wooden floor has meant that all nests are inside the box and not under the floor as happened with some nest boxes in the previous two years. A total of 40 nests were recorded and the success rate was high with ca 70% of birds ringed as nestlings being retrapped as juveniles.

In the 1998 season we caught 92 adult males and 52 adult females, In previous years there has been a small excess of males, but never to the extent recorded last year.  This year to date of the 166 juveniles ringed 101 are males. The imbalance has been especially marked in the third brood, with 25 of the 35 being males. Why this should be so is interesting Dr. Ian Hartley from Lancaster University (remember he gave us the fascinating talk on dunnock behaviour). He has taken DNA samples from almost all the successful broods to see what the sex ratio is in the nest. Male bearded tits are about a gram heavier than females so perhaps they survive the winter better than the females. A limited analysis of our ringing data does suggest that males live longer than females but we really need more data.  To date this year we have caught 43 adult males and only 14 females but we will catch many more adults during the autumn but the early indications are that the preponderance of males is continuing.

This year we have individually colour ringed all birds caught as part of the above DNA study. So if you see beardies away from Leighton look carefully for rings, each bird has four rings on and it is important to record the position and on which leg the BTO metal ring is located. If you want to see bearded tits at their best we have Bearded Tit Watches on Sunday October 3rd and 10th. Otherwise pick a calm morning in October and visit the Causeway between 09.00 and ca 10.30.

John Wilson

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