Variant Chiffchaff calls

Chiffchaffs Phylloscopus collybita call normally in Finland as in Western Europe - the calls of the nominate subspecies and abietinus are similar, which is well mentioned in the literature.

The call is like this:

(1.) Hanko, Uusimaa, Finland 6 October 2007

During spring, the call is the same:

(2.) Ridala, Läänemaa, Estonia 30 April 2005

And the calls are similar in southern Finland (where the species is somewhat uncommon as a breeder, but more common during autumn migration) and northern Estonia (where the species is one of the most numerous breeding passerines).

The call of Chiffchaffs was normal during the autumn of 1998 in southern Finland:

(3.) Hanko, Uusimaa, Finland 3 October 1998

But in Estonia, it was quite different (Chiffchaffs calling like this were very numerous at the time):

(4.) Nigula, Pärnumaa, Estonia 29 August 1998

The next autumn the strangely calling Chiffchaffs also occurred in Finland causing lots of discussion:

(5.) Helsinki, Uusimaa, Finland 26 September 1999

The most interesting thing was that the almost all Chiffchaffs called like this. I had difficulties finding any normal Chiffchaffs during the autumn of 1999, although Pöyhönen (2000) reported hearing several amongst the strange calling birds. The strange call reappeared in the next spring (Pöyhönen 2000) and also in the autumn of 2000, both in Finland and Estonia:

(6.) Sörve, Saaremaa, Estonia 16 September 2000

Although many calls heard earlier during the autumn were somewhat different:

(7.) Noarootsi, Läänemaa, Estonia 14 August 2000

I personally heard the last Chiffchaffs using the 1998-2000 call in the spring of 2001 in Estonia. By the next autumn the call had changed:

(8.) Vasknarva, Itä-Virumaa, Estonia 25 August 2001

And the next autumn:

(9.) Espoo, Uusimaa, Finland 22 September 2002

After that the calls have been of the old standard type from year to year.

The aberrant calls were not confined to Estonia and Finland:

(10.) Mamaia, Dobrogea, Romania 3 April 1999

(11.) Slava Rusa, Dobrogea, Romania 14 October 2000

The years 1998-2001 was not the first period when these kind of calls were heard in Finland. They also occurred in the autumn of 1988 and 1993 (Pöyhönen 2000, own obs.). During 1999 there were lots of discussion about the origin of these birds. In any case, they were far too numerous to be accidentals from far away. They were very similar in appearance to normal Chiffchaffs (Pöyhönen 2000, own obs.). Constantine et al (2006) described these kind of calls and judged them to be the normal juvenile call of Chiffchaff. While this may be true in Western Europe, it is not in Finland and Estonia, where juvenile Chiffchaffs do not use this kind of call in normal years:

More recordings from early autumn in Estonia.

After several more years of listening and recording Chiffchaff calls, I think that this kind of calls are a variation of call of normal Chiffchaffs, which just are "in fashion" in some years. The call is variable both within and between years, more variable than the normal call, the fact which Constantine et al (2006) thought was a mark of plasticity of the juvenile call. Most probably the birds learn to use it from each other. I don't know why they start to use it and why it becomes so widespread.

Literature:

Pöyhönen M 2000: Poikkeavasti ääntelevät tiltaltit. Linnut 3/2000.

Constantine M & The Sound Approach 2006: The Sound Approach to birding.

Newer publication here.