Reed Warblers Move Out

The re-trapping this morning (9/9) of an adult Reed Warbler may not at first sight appear unusual, but is is only the sixth adult to be caught in September in the 12 years study of the Reed Warblers of Leighton Moss in which we have ringed 13701 birds.The bird was a female still with a very marked brood patch.Our catching and recovery statistics shows that adults start to leave in late July and on through August. Totaling the 12 years we have handled an average of 485 adults in each of the three ten day periods in July. By early August this had dropped to 316, and during the second 10 day period to 108 , then just to 53 in the last ten day period. Showing a marked move out over the period.

To further support these findings we have had 18 adult Reed Warblers controlled on the south coast of England on migration, the bulk at Icklesham in Sussex. Of these four were in the last few days of July, ten spread though August and just three in September. Juveniles remain quite a bit later, with the period late July through August giving the largest catches. Early September sees a slight decline, followed by much lower numbers through to early October. Recoveries of juveniles on the south coast also peak later than the adults with the most in the last 10 day period of August and early September but with some birds turning up on through to late September. The adult female caught today was obviously a late breeder.
John