WILLOW WARBLER (Phylloscopus trochilus)

Pouillot fitis

 

The Willow Warbler is a summer visitor to Switzerland from late March to early October, and occurring usually only below 1000m. The southern limit of its breeding range cuts right through Switzerland and this bird is only found in the northern plateau, the Jura and the northern slopes of the pre-alps. It is not found in the alps nor south of them except on migration.

In the field it is very hard to distinguish from a Chiff Chaff, the latter having black legs whereas a Willow Warbler has brown legs. However the song immediately tells them apart - the rhythmic "chiff chaff" song is replaced with a series of warbling notes that meander down the scale:

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(Yes that was a Wryneck calling the background).The notes slowly descend the scale, some often repeated 2-3 times and towards the end the notes tend to finish with an upward slide, especially the final note giving the impression of a very flowery finish to each phrase. This can be seen in the sonogram:

Like the Chiff Chaff however it also gives a single note call - "hooweeet" with which it can be confused. However the Willow Warbler call is a level note which rises at the end giving the impression of two syllables. Unfortunately the only recording I have of this is a rather poor one with a "hissy" microphone but let's listen to it anyway as it will help separate these two birds even with their simple calls:

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The sonogram shows quite clearly the extended opening part of the note which is level with a rapid rise at the end - "hoowheet":

The Chiff Chaff call on the other hand is a continuously rising note - here are the two side by side, first three Chiff Chaff calls then two Willow Warbler followed by three more Chiff Chaff:

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and in a sonogram:

So even though these two are very hard to separate visually, careful listening can give certain identification.

 

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