Willow
Warbler Phylloscopus trochilus is a common spring passage and uncommon
autumn passage migrant through Sabkhat Al Fasl that is scarce in the summer and
rare in the winter. This is a change in status from Peter Symens &
Abdullah H Alsuhaibany, study from May 1992 until May 1995 where they were
recorded as Abundant. They are a long-distance migrant passing through the site
in late spring from late March to early June and again from mid-August to
October where they occurred in reeds, bushes and trees anywhere. Their
migration period was later than Common Chiffchaff P. collybita in
spring, with a short overlap period occurring in the last week of March and the
first week of April, and earlier in autumn. Peak passage occurred during 10
April to 2 May with the latest bird trapped in the spring being 7 June. Some of
the birds caught in spring had extensive amounts of fat present indicating they
had fed well at the location and were about to move on. Two or three
sub-species appear to occur at the site with one being the smaller, more
brightly coloured olive-green and yellow nominate P. t. trochilus that
breeds in Ireland, Britain and Southern Sweden south to northern Spain, central
and north-west France east to Southern Poland and northern Romania and winters
in sub-Saharan west Africa that was a common passage migrant. The Willow
Warbler is a very variable species with as much variation within races as there
is between them and are clinal across their range with acredula being
very variable and intergrading with yakutensis in Siberia which was
reflected in the other type seen that was the larger P. t. acredula /
P. t. yakutensis. P. t. acredula breeds from Scandinavia, except
southern Sweden & central and east Europe to central Siberia and
winters in Africa south of Sudan and was a scarce passage migrant. Some of
these birds were not very distinctive and most probably referred to acredula
with the large, bulky, very brown/grey and white birds with yellow fringes to
the secondaries being either P. t. acredula / P. t. yakutensis.
These had wing lengths of greater than 73 mm and tail lengths greater than 56
mm and occurred in the first week of May, slightly later than the first wave of
P. t. trochilus. P. t. yakutensis breeds in central and east Siberia
and winters in east & South Africa and were the largest and palest
race, showing virtually no yellow and very little green in their plumage, and
were paler brown above and white with a greyish wash to breast. The rump and
fringes to the retrices and remiges showed only a trace of olive-green and the
supercillium was almost white and they had smaller bills and occasionally some
streaking on the throat and upper breast. This makes it difficult to assign
birds to certain races unless a clear distinctive example can be found which is
best done on size and colour, but only fresh plumaged birds should be
considered. Below are photos of presumed trochilus,
acredula/yakutensis and acredula
type birds.
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| trochilus type |
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| acredula type |
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| acredula / Yakutensis type |