Monday (14 May 2018) at about 07:45, I found a very interesting
warbler at Noordhollands Duinreservaat, Castricum,
the Netherlands. The first song phrases I heard were similar
to Western Bonelli’s Warbler. But then the bird started singing another
song type, including a few introductory notes as in
Wood Warbler. A bit confused and thinking it was probably just
an odd Wood Warbler, I tried to see what the bird looked like. As it was
singing from a small patch of oak trees, using exposed song posts and
flying between them at c 2-3 m above the ground, it did not take
long to get proper views. Shocked by the fact that it also looked
cross between the two species, the 'hybrid option' then seemed the only
logical explanation. I decided it was time to inform other birders.
The bird was studied by several birdwatchers (for example, see here
Hans Schekkerman's clear observations and extensive description) and is
today (18 May). On the evening
of 15 May, it was trapped and ringed by Tim van der Meer and Jan
Visser. Biometrics were taken (for example, a wing length of 73 mm) and
a feather was collected for DNA analysis. Obviously I am
very much looking forward to seeing the results!
To be continued...