Phylloscopus trochilus This picture is taken at the bird observatory area. Photo: Jan Erik Røer
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The Willow Warbler is a migratory bird that breeds all over Norway and the rest of Northern and Central Europe. It prefers deciduous forests and is found everywhere from gardens to willow bushes in the mountains. The Willow Warbler is very numerous. It is an insect specialist and migrates at night, travelling to the sub-Saharan Africa in winter. It mostly arrives at Lista in April - May and returns in July - August. Ringing recovers have shown that the populations present at Lista probably breed mainly in the western side of Sørlandet (southern counties) and southern Vestlandet (south-western counties) from Norway, following a western migratory route over the Iberian Peninsula with a wintering area far west in Africa.
The Willow Warbler's movement pattern is low in the vegetation. This together with the fact that it is very common, makes it a good species to monitor in the standardized ringing. At Lista Bird Observatory there are a few local breeding birds. However, a large part of the early ringing in autumn (which is a significant proportion of the total ringing) is young birds that have not finished moulting. Birds that have not travelled long distances. The Willow Warbler shows a tendency to arrive earlier in the spring than it did before at the bird observatory .
There was use of playback in the autumn in the first years 1990-93. Therefore, those years have been removed from the standardized material. The autumn standardized monitoring for this species applies from 1994.
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Figure 1.Total number of recorded observed Willow Warblers.
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Figure 2.
The phenology of all observed Willow Warblers has a marked peak just before mid-May. The main part of the autumn migration passes from the last third of July to the end of August.
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Figure 3.There is considerable variation from year to year in the figure, but no marked trend.
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Figure 4.The autumn ringing has a high proportion of young birds, so it is natural to think that the variation between the years is an expression of the young production and that this varies considerably. It is worth mentioning that the low years 2003 and 2007 were just as bad in the spring as well, while it was the opposite for 2004 with high numbers in spring and autumn.
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Figure 5. The phenology from the standardized ringing in spring shows that some birds can come in early April, but that migration really starts by the end of the month.
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Figure 6. The average median date is 10 May.
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Figure 7.
The phenology of the autumn migration shows that in most years the Willow Warbler is caught as soon as the ringing campaign starts.
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Figure 8.
The number contains a proportion of local birds which can be significant, making the period 10-90 % longer. Median date is August 7.
. An adult bird in the lighthouse garden with white (slightly yellow) markings and dark legs.
Photo: Gunnar Gundersen
. This Willow Warbler was photographed at the lighthouse area on 04.08.2013. It is a young bird which has not moulted the body feathers yet. It is photographed the same day as the bird on the top of the entire presentation (with ring).
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