This Spring there appear to be exceptional numbers of Chiffchaffs uttering a so-called ‘alternative call’ i.e. the downward inflected ‘sweeoo’ note. This call has in the past been ascribed to autumn juveniles, with frequent statements that it is not heard after late-October. This is erroneous, as it can be heard throughout the Winter and in the Spring (as noted in BB (2010) 103: 325). Observers are now more alert to the alternative ‘sweeoo’ call than a few years ago. Nevertheless, the number of ‘sweeoo callers’ this Spring does seem to be exceptional. In the West Midlands in the past ten days (pers obs) around 40% of Chiffchaffs heard calling have used the ‘sweeoo’ call, with a clear majority today (April 15th). In Dorset, Grahame Walbridge has also noted a high incidence of ‘sweeoo’ callers. Unlike in previous years, Chiffchaffs uttering a ‘sweeoo’ call this Spring have also attracted John Martin’s attention. A few of these ‘alternative callers’ have used a truncated, more monosyllabic version of the call i.e. ‘swee’, the version which most readily invites confusion with Siberian Chiffchaff’s call. One or two individuals under close observation have switched between the ‘sweeoo’ call and a conventional, upward inflected ‘hüit’ call. I would be interested to know whether observers in other parts of the UK have noted a high incidence of ‘sweeoo’ callers this Spring.