As a Portuguese birdwatcher, Arctic warbler has been, for a long time, a most wanted bird and one of the rarities that one wishes to tick.
So far there’s only one accepted record in Portugal. In 2009 (September 28) a juvenile was ringed in Santo André lagoon by Carlos Pacheco and others (see here).
This species winters primarily in Malaysia, Phillipines and Indonesia.
I’m currently in Java, and the opportunity to observe and study Arctic Warblers in the wintering grounds seems irresistible.
But here arises a problem…
Arctic Warbler has now been split into three cryptic species due to differences in genetics.
The split was proposed in 2011 in the following paper: “Alström, P., Saitoh, T., Williams, D., Nishiumi, I., Shigeta, Y., Ueda, K., Irestedt, M., Björklund, M., and Olson, U. (2011). The Arctic Warbler Phylloscopus borealis– three anciently separated cryptic species revealed. Ibis 1532: 395–410”, an abstract of which can be seen here and here.
According to this paper distinguish these three species will be impossible by plumage alone, leaving us with calls and songs as the only safe method of ID.
On February 7, 2015 in Bogor Botanical Garden a warbler caught the attention.
Plumage and structure seemed to be typical of Arctic warbler, although much greyish in tone than a previous bird seen at the same place, identified as Phylloscopus borealis (photo here). But as we already know plumage is of little use in the field.
Fortunately it was calling and I managed to get this recording:
The double note call seems to indicate Phylloscopus examinandus. Looking at the sonogram we can see two syllables:
If we compare to the example in the previous paper we can see similarities:
On March 18, 2015 an Arctic warbler Phylloscopus borealis was recorded at the same place. It was much silent than the previous bird. Only calling randomly, a single note call:
The sonogram shows one sillable:
Comparing with the sonogram in the paper we can see the same pattern:
Today I managed to record another Arctic warbler P. borealis, a single note call given when I approached the bird:
I would like to hear some inputs on these observations, especially on the recording of P. examinandus.