This juvenile bird has been captured and ringed by Thijs Valkenburg on the 04-08-2010 near Silves (West Algarve).
It shows all characteristics (and biometrics) of Hippolais opaca (Western Olivaceous / Isabelline Warbler) - a species that is an extreme rare breeder in the country.
I have heard and observed a Isabelline Warbler in May with clients near Faro (bird was on passage) and a friend of mine managed some record shots the same day (see the blog-entry here).
The bird moved on and the photos led to some discussion, because some features, namely the undertail coverts (quite long, not white, graduated rectrices ?) did not look so "ideal" (at least compared to illustrations, like in Svensson et al.)
So, now again an opportunity to compare - the undertail coverts fit ! Also the broad bill base JT pointed out on the bird seen in May.
Photos: Thijs Valkenburg, 04-08-2010, Silves (West Algarve).
A nice video of an adult bird in hand is here.
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