Summer Birding: Acros - Marsh Warbler

Hi all,

Acro warbler's for some people are just a 'No No' to go into identification. Most warbler's that look like a 'Reed' warbler are noted as a Eurasian Reed warbler. But for some of us we like to delve deeper into the identification of the acros which can be a bit of a head wreaker!!! (Give me a Blue-headed wagtail any day!). 

So, on the 27th of June I came across a juvenile Little ringed plover (Still a decent rare bird in Ireland), on my patch Chore Marsh, Co. Wexford. While photographing the bird flying overhead calling I watched it drop into a muddy area beyond the start of the 'Central' reedbed. So accordingly I walked over to this patch which cuts through the reeds and has a channel on either side. Not managing to relocating the LRP after about an hour searching I was just at the end of the track to head back to the original LRP site I heard a warbler singing it's heart out, didn't sound right for a Reed warbler. So that got me thinking, the mixed up and lack of repetitive notes within the song struck me! Could this be a Marsh Warbler ?! I had to be careful calling this bird as up until then there had only been 6 previous Irish records! It was going to cause a bit of a twitch!

Marsh Warbler (Acrocephalus palustris) - Image by Cian Cardiff

Before putting the news out I was sending out some sound recording of the warbler in question to a few friends for the thoughts. On the 5th occasion the bird began sing it started to rise up out of the reed-bed enabling clear view of the acro in question. So I got the camera onto it and managed a couple of 'Proof of Life' images. (Attached).

On first inspection of the images I could see the sharply edged white tips to the primary tips which we all knwo to be a distinctive feature of Marsh, which as you can imagine got me hyped up! So then, lets get down to business on the feature's that lead to it's Identification as Irelands 7th Marsh Warbler:

Marsh Warbler (Acrocephalus palustris) - Image by Cian Cardiff

Cahore Marsh warbler Identification feature's :
  • Bill - Thick, with a sharp tip. Complete yellow lower mandible which was a feature that really got me thinking of marsh.
  • Eye-ring - Lack of a white eye ring, unlike that on most Eurasian Reed Warblers during summer which show a clean and striking white eye ring.
  • Head Shape - While singing the crown feathers where like a punk hair style! All spiked up. As was the throat, puffed out white feathers.
  • Mantle Tone -  A very smooth and rather like fine 'sand' as I explain it! Extremly clean feathering.
  • Breast & Underparts - Faint creamy colour tone to the breast band and clean white underparts.
  • Tertials - A nice darker brown wash with a lighter brown fringing around them.
  • Primaries - BINGO! 8 primary tips, a feature of Marsh warbler! And believed to be a diagnostic feature compared to under 8 for Eurasian Reed Warblers! Plus the fact that the primaries showed 8 white tips! Something I have never seen on a Eurasian Reed Warbler before in Ireland.
Marsh Warbler (Acrocephalus palustris) - Image by Mark Steward
  • Tail - Long with notiching within the tail! Rumoured to be a feature of Marsh I hear. 
  • Legs -Green/Yellow wash unlike that of the grey Eurasian Reeds.

We had came across a very striking and pale Acro that eveing and it took use a while to rule out it being the Marsh, but we did after seeing the white eye ring, plain brown primary tips, and then bill and greyish leg colour. But this bird was super to learn off, due to it being so 'Sandy' brown in colour (Like a Marsh or even a Caspian Raced Reed warbler which I had seen a piece wriiten on by the Birding Frontier's guys) . But with some shots of this bird I was happy to call it a Eurasian Reed warbler. The song is just such a classic feature of the marsh warbler, but do be aware of late arrived Male reed warbler's singing like marsh warbs looking for a mate! The marsh mimicking other bird species is something thoroughly special to hear on your local patch! And to get sound recording of!

Marsh Warbler (Acrocephalus palustris) - Image by Mark Steward

So after all that and some good sound recording and photographs in the coming days I had nailed Ireland's 7th Marsh warbler! Happy days indeed and I hope this will give more confidence to birder's to work on acro identification; also many thanks to Mark Steward for his epic shots of the bird!




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