Monday, 28 March 2011

Marsh harrier Madness

Just before I went away to Wales for a week I pitched an idea about Marsh harrier age and moult. Marsh Harriers have bred in Weymouth since 2009 when a pair settled at Radipole. At the time it seems these birds caused a little confusion regarding age of the birds and also their sex! This sounds a bit crazy given the amount of time people spent watching them but speaking to different birders in the area, nobody seems to agree on anything. I replied to message correcting a mistake made by a local birder. The male from last year is breeding again this year but it was called a 2nd calendar year bird. This clearly can’t be the case. Easy mistake to make though, as calendar years catch quite a few people out. In the same message I thought I’d post a few ideas with regards to this bird’s plumage. A well respected local birder seemed to think it was a perfectly good theory, so I thought it would make an interesting discussion. Sadly, the topic went a little off topic and deteriorated rapidly. Though a few did have worth while things to say.

This is our current male who’s spending quite a bit of time at Radipole at present. I suggested the theory that this bird could be a ‘dark morph’ male Marsh harrier. At the time of posting I hadn’t had a particularly good view of the bird and just remember this bird as being completely dark on the back from good views through the winter. The concept of a dark morph bird was completely dismissed by local birders nobody could find any literature on this. As Marsh Harriers are quite a new thing to me I consulted a few ‘experts’ to find sensible answers to a few questions. After spending countless hours at Lodmoor last year I am really interested in finding out more about this superb species. I had a response from Gerd Heinze who’s a German expert on Marsh harriers. I also had a response from Javier Blasco-Zumeta who has a super website . They confirmed that there can indeed be dark male Marsh Harriers and it did cross their minds when looking at this bird. In the end they both concluded that this is within the individual variation of a 3rd calendar year male in spring. This is the opinion of several local birder though it’s a shame that proper discussions can’t be had via internet forums to discuss things sensibly. From the emails exchanged over the last few days I’ve learnt a lot of about Marsh Harrier aging and have found it fascinating as any ringer/birder would. After all, ringers spend most of their time aging birds and looking at moult, sticking a ring on a leg is the easy part!
 Here’s some more shots showing the very slight hint of grey in the primary coverts, though its very subtle and is very much influenced by the light. However the tail is but more obviously pale and slightly grey. Will be interesting to see how he turns out this autumn.

The bird below is the female that’s showing different generations of feathers in the wing. It think 'we' are considering this bird to be an adult. Three age groups can be recognised in female Marsh harriers, Juv, 2nd year winter/3rd year spring and Adult. Like I've implied before, I am no expert on Marsh harrier aging so if you think this isn't an adult please say!

It’s truly amazing to see these birds in the middle of Weymouth. Saturday’s views were particularly incredible as they were in full display and even grasping talons. I really can’t get enough of these birds!


  1. I totally agree Luke mate, there's clearly a moultt going on but that pantomine of out and about numpties are obviously that depressed they need to put you down. What sort of longevity can dark morph plumage last? Ie can you get dark morph immatures that mould into light morph adult plumage? Sorry sorry getting far too interested in Marshy moults haha!
    And dissing the RSPB! Oh dear change the record (not you Luke, those twits on that ego forum). I wonder whether Marsh Harriers, Otters, Beared Tits, Cetti's Warblers, Bitterns would be safeguarded in the middle of Weymouth without you!? And how many recent rarities on the resereves recently...hmm keep up the good work!

  2. Good to hear from you mate! I would imagine a dark morph bird would be dark for life. Same principle as a dark morph monties.
    Nobody can doubt that the RSPB have improved the wetlands around Weymouth a hell of a lot. Most local birders know that and certainly appreciate it, but there's always the odd one. But hey... people love to have a moan, its human nature. As long as we know we are doing the best we can!(though cutting down sycamore is a bit to far apparently! Lol!)

    hope all is well on Fair Isle!

  3. That was a helpful reply from Blasco-Zumeta and good of him to get a second opinion from Heinze. Like you, I'll be very interested to see how this bird emerges from the summer moult - let's hope it does the "right" thing.

    With such subtle details being so important it's a shame that so many of the images are of distant birds and that the photo-record since April 2009 has so many gaps.

    However confusing it is sometimes, I agree totally that it's a great experience watching these birds perform against an urban background and that they keep coming back!