WOOD WARBLER (Phylloscopus sibilatrix)
I always feel that winter is finally over and that the
spring is properly under way when I hear Wood Warblers singing. As the name implies it is a bird of
woodlands, but in Switzerland of broad leafed woodlands and it is found throughout suitable habitat in the lowlands mostly below 1000m.
It is a member of that tricky family the Phylloscopus warblers and in our region can easily be confused with Willow Warbler and Chiff Chaff, not quite as similar as it is fairly yellow on the throat and upper breast, and like those other two it has a very distinctive song that immediately identifies it.
The most commonly heard is a series of “pit” notes that start rather slowly and accelerate until individual notes can no longer be distinguished, the rhythm makes me think of a bouncing ping-pong ball:
This is a bird that puts its all and everything into this song and when it reaches the crescendo it quivers its wings and body as if in ecstasy.
But it also has another song which is used less – a series of rather plaintive “pluie” notes, unlike the “bouncing ball” song this is not usually used repeatedly but seems to be thrown in every so often as if to change the rhythm. Here the “pluie” song sandwiches the other one, then I have cut a third in for reference purposes, you can also hear another one answering in the distance:
This song is an easy one to whistle and the bird will come and investigate if you do so.The Willow Tit makes a similar song and could be confused with this, here comes 2 sets of Willow Tit followed by 3 Wood Warbler then 2 Willow Tit again:
and the sonogram of the same, it can be seen that the Wood Warbler descends more quickly and is slightly lower and more sorrowful in tone:
This exact same note is also used individually as a call note and Sample (2010) says this is a contact and alarm call, and indeed I recorded this when two birds seemed to be having a territorial dispute:
You can hear that it nearly started the bouncing ball song in the middle there, (and that was a Green Woodpecker calling in the background). If we examine the call note you can see it is the exact same shape as that used in the “pluie” song:
So put all this together and you can end up with a sound scene like this:
A snatch of a Great Spotted Woodpecker in there at 20s, and also assorted gunshots ! You can now understand why the French name sifleur means "whistler".
A NOTE ON POSSIBLE CONFUSION: It is possible to confuse the song of the Willow Tit with the "pluie" song of the Wood Warbler. To my ears the Willow Tit is slower and more deliberate, the Wood Warbler slightly faster, and for reasons I cannot explain sounds a bit more plaintive. Here is a mixed file of three Wood Warbler, three Willow Tit song sequences, then three Wood Warbler again:
If you review the sonogram of the first part of this same file you can see that the Wood Warbler (first three) descends much faster and is delivered more rapidly than the Willow Tit (the second three):
(NB: the timing between phrases (but not the notes) was shortened in those to make the files smaller)