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Status/distribution
The
Willow Warbler is our commonest summer visitor. They are
distributed throughout Britain and Ireland, except in treeless
uplands and islands. They can occur at high breeding densities
in some habitats such as Scottish birchwoods. Long-term census
data shows a rapid decline in the 1980s after 20 years of
relative stability. Further investigation showed that the
decline only occurred in the south of the UK and was driven
by falling survival rates. Willow Warbler populations in
Scotland were unaffected.
Detailed
information on Willow Warbler population trends and breeding
success is given on the Wider
Countryside Report web pages.
Timing
of migration
Male
Willow Warblers arrive ahead of the females to set up territories
and are generally recorded from mid-March onwards. Peak arrivals
tend to occur in late April or early May. Information from
bird
observatories suggests that most Willow Warblers arrive
on the south and south-west coasts rather than on the east
coast.
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