Sweeoo Chiffchaffs in Finland in 2011

In 2011, the first time since the autumn of 2000 (for more information, look here) the variant call of Chiffchaff, the so-called sweeoo call, was common in the Helsinki area in Finland. During the spring and summer I heard only normal calls but in autumn sweeoo calls greatly outnumbered the normal calling birds.

Vermo, Espoo, Finland 19 September 2011, spectrogram below

We also trapped many birds at our normal ringing sites. Between 11 September and 9 October I personally ringed,measured and photographed 45 Chiffchaffs at the Laajalahti ringing site, and of these, 18 called in the hand or immediately after release, all using the sweeoo call. One of these 18 was identified as an adult based on fresh rectrices with rounded tips. William Velmala also ringed one adult with a sweeoo call.

The bird below (38367U) was ringed on 17 September 2011. The wing was 61 mm and the wing-formula 6/0/0/0/2/5.5/7. These measurements and all other characters were very normal for Chiffchaffs in this area.

It called like this, the spectrogram is shown below.

The bird below (29843U) was already ringed when trapped 9 October 2011. Wing length 61mm, wing formula 5.5/0/0/1/3/6/8.5

It called like this, the spectrogram is shown below.

The sweeoo call was also dominant in North-Western Estonia this autumn. This call was recorded on 25 Septermber 2011 at Haversi, Noarootsi, Läänemaa. The spectrogram is shown below.

See also here.