As one might expect, the bulk of Yellow-browed Warblers occurring at Nanjizal have been during October. Up until the end of 2020 there had been just two spring records, an overwintering bird re-trapped on 22 March 2016 and a bird in heavy body feather moult was ringed on 7 April 2017. The number of birds ringed each session, month and year is variable, and this variation is indicated by the black Standard Error (SE) lines in thegraph below.
In total, 269 Yellow-browed Warbler have been ringed at Nanjizal. Whilst only 38 had been ringed during the seventeen year period up to 2013, 107 were ringed during 2016, nearly five times the previous highest annual total of 22 (in 2015). This included twenty birds ringed on October 12th 2016 alone. As far as we are aware, this is the largest annual ringing total for the species at any site in the UK. Numbers at Nanjizal do not seem to be dependent upon easterly winds, and high totals are often associated with light westerly winds- perhaps birds actively migrating west are held up by the headwinds.
During 2020, 40 Yellow-browed Warbler were ringed, the second highest annual total, though once effort was taken into account 2020 was slightly behind 2017 in the number of birds ringed per session.
Similar increases in numbers have been observed recently across the UK and indeed Western Europe, though autumn 2016 was characterized by prolonged periods of easterly airflow which is likely to have further influenced the high numbers that occurred at Nanjizal.
A Yellow-browed Warbler ringed at Gibraltar Point in Lincolnshire on October 3rd 2015 was re-trapped at Nanjizal on October 10th, a distance of 536 km. A second recovery involved a bird ringed at St Abbs Head in Borders on October 9th 2016 and re-trapped at Nanjizal on October 31st 2016, a distance of 694 km.
The breeding and wintering distribution of Yellow-browed Warblers from HBW Alive can be found here.