Juvenile Marsh Warbler? (Netherlands, Oostvaardersplassen, July 14th, 2023) (1 Viewer)

[Frank-birding]

This afternoon I saw this young bird. (Netherlands, Flevoland, Oostvaardersplassen) It was relatively tame, and actively foraging on and near a path. When disturbed by a passing mountain biker, it was back in no time. It was near both reeds/high grasses and forest/trees/scrub. Its blackish and baldish head confuses me, otherwise I'd think maybe a Reed or Marsh Warbler (probably the latter, judging by the colour of its legs). Although very tame in its behaviour for either one.
Could somebody tell what bird it is?

Regards, Frank

 

[Alexander Stöhr]

Hello Frank,

I agree with you and Ken. Its a Marsh/Reed Warbler for me too.
This poor bird has lost most of its head feathers, hence the strange look and the massive bill (where parts are normally hidden below feathers).

Plesase note, that this is an adult bird imo.

Caveat: no offence you know: I would like to know, if a Reed Warbler can ruled out with confidence here. A Reed Warbler with a similar leg colour is here:

https://flic.kr/p/2m1TLhf

(16.05.2021, Schwetzinger Wiesen, SW-Germany)
all: Teichrohrsänger SW

 

[Frank-birding]

Thank you Alexander (and Ken, Lou and Bewick) for looking into this!

Yes, it's not a young bird. You're right, it's strangely moulting or something other is awry with its head feathers. Fortunately the bird seemed in good health otherwise, it was actively searching for food, catching many an insect and was able to fly. (Although its relative tameness is maybe a sign that it has to take risks when foraging a completely healthy bird wouldn't have to take.)

Interesting, this Reed Warbler with yellow-greenish legs! Observations like these make ID-ing silent Marsh vs Reed Warblers even more difficult than it already is

Regards, Frank

 

[lou salomon]

those are feather mites causing such a bald appearance. 'Swollen' lower mandible and blunt tip remind more of a Marsh Warbler but primary projection looks shortish for that. legs look pale to me, but not greenish at all. Can't really identify it.

 

[CARERY]

A strange looking bird... Even if rather unlikely in The Netherlands, I wonder if, given the short primary projection, one should consider Blyth's Reed as well? A pity we can't assess it's face pattern and it seems to be a really long bill (even after taking the missing feathers into account).

 

[Frank-birding]

those are feather mites causing such a bald appearance. 'Swollen' lower mandible and blunt tip remind more of a Marsh Warbler but primary projection looks shortish for that. legs look pale to me, but not greenish at all. Can't really identify it.

Ah, its suffering from feather mites. Good to know. Then, despite its still active behaviour, the unfortunate bird is probably doomed.

 

[Frank-birding]

A strange looking bird... Even if rather unlikely in The Netherlands, I wonder if, given the short primary projection, one should consider Blyth's Reed as well? A pity we can't assess it's face pattern and it seems to be a really long bill (even after taking the missing feathers into account).

We've had quite a number of Blyth's over the last 2 months or so, not out of the question, but very rare indeed.
Still, Blyth's seems a good fit (bill shape as well), also its foraging behaviour on the gound (if not influenced by the mite infection, a big if) fits Blyth's much more than Marsh or Reed. Perhaps the leg colour is too light and the bill is too orange (without any black associated with Blyth's)?

 

[jalid]

Yes, the bird is an adult. I think that the appearance of the head is part of normal moult. I see this kind of heads quite regularly in adult Eurasian Reeds, and sometimes also in Marsh Warblers. I do not remember ever seeing it in Blyth's Reed Warbler. I think that colour of the legs, emarginations and alula colour confidently rule out Blyth's Reed. I am not really sure whether it is Marsh or Reed - leg colour is better for former, but shortish primary projection and shortih tertials for the latter.