Large numbers of Reed Warblers are ringed each year at Leighon Moss during our Bearded Tit study. Since 1997 we have registered this ringing in the BTO's RAS scheme which attempts to monitor the survival of adults. With the ringing effort being roughly similar each year we get an idea of population levels as well.
Our average catch of adults in the 12 years from 1997 to 2008 is 176. This year to date we have recorded 166- slightly below average but 13 up on 2008. We may yet catch a few more although most adults appear to leave during the period late July and through August. In the 12 years studied we have only recorded 5 adults in September, although many juveniles are caught in the first half of September.
Reed Warblers appear to be long-lived. This year we have caught one first ringed in 2002, 4 in 2003 and 1 on 2004. This year adults seem to have stopped a little later than usual with 9 adults caught between August 16th and yesterday(25th)- in some years we have not caught any adults at all in this period. Of the 9 adults caught this year 5 were well above the average weight of 11 grams with the heaviest being 14.3 grams. These 5 all showed signs of laying down fat reserves in readiness for migration.
Recoveries from our ringing give some clues as to the timing of this migration. We have had 11 adult Reed Warblers caught on passage along the south coast of England the earliest was on August 2nd and most were during mid August. Tracking the migration further, our earliest date for an adult on migration along the Atlantic coast of France is August 10th.
We also monitor productivity and this year seems to have been well up to average with 430 juveniles ringed to date.