Wednesday 10 April 2013

Michael Cobley's Bird Of The Month - April

Bird of the month – April
If March is a rather quiet birding month then April is quite the opposite. This is the ‘real’ and easiest month in which to observe bird migration in action. Most of our trees will not have their full cloak of leaves, and seeing birds in the branches is not too difficult. The first job of our male summer visitors is to establish a territory to which they can attract a mate, and which will provide a good breeding area in which the pair can and raise a family. The males do this by singing and displaying, and one of the most common birds singing now is the Chiffchaff. Their song cannot be confused with any other bird and to hear the first of the year is a delightful treat. Very often the first indication of their presence is a bird singing in the upper branches of a small tree. I must add that their monotonous song can soon become a bit wearing and we soon treat it as background noise. I much prefer the song of the closely related Willow Warbler but Chiffchaff is truly the bird of April. 

We have a very small number of birds which stay with us during the winter instead of migrating to the Mediterranean and North Africa, but they are seldom seen and of course they do not sing. They spend most of their time trying to find enough food with which to keep them alive, their strategy being that if they do make it through the winter they will have a head start in establishing the best territories before the hoards of competitors arrive. They will be in far better physical shape (flying from Africa really takes it out of you), and so for the survivors it will have been worth the risk. These wintering Chiffchaffs are best found in coastal reed beds – coastal because that is where it is warmest, and reed beds because they provide the most insects on which the birds feed. A few years ago whilst ringing with mist nets on one such reed bed we trapped perhaps 10 birds over a period of three weeks. We did not see any other than those which we trapped, and only then when they were caught in the nets. ‘Normal’ observations would have led you to believe that there were none present.
So how do we tell a Chiffchaff from a Willow Warbler? Well its difficult! Apart from their songs which are unmistakable there are some other clues. Willow Warblers ‘GENERALLY’ have pale legs, a slightly cleaner and brighter appearance, the yellow is more yellow and the green more greener; they are also slightly larger, but most of all they hardly ever dip their tail when perched. Chiffchaffs frequently dip their tail. But what about a bird that does not dip its tail but looks like a Chiffchaff ?– well you just have to look for some other sign or wait for it to sing!
Most of our summer visitor warblers spend the winter in sub Saharan Africa and do not reach us as soon as the Chiffchaff so this warbler is the bird of the month for April.
Mike Cobley

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