Portlandia

I've run away from London for the weekend and I'm spending a bit of time at Portland Bird Observatory in Dorset.


We started the morning with a few hours of ringing. We ringed just two birds, though they were interesting and unexpected, respectively. First bird in the net was a 2cy Song Thrush that had undergone a really extensive post-juvenile moult last year.


It had moulted all median coverts, the inner nine greater coverts, the carpal covert and A1 on both wings, plus T1 on the left and T1–2 on the right. Although I'm used to seeing birds in Scandinavia with quite limited post-juvenile moult (usually just a few greater coverts and often not even all of the median coverts moulted), this bird's moult was extensive even by British standards; it's by far the most extensive post-juvenile Song thrush moult I've seen.


Usually, I assume any replaced tail feathers in thrushes to regrowth following accidental loss. However, the new R1 on the left hand side on this bird I suspect might be part of the post-juvenile moult. It certainly fits the pattern for “normal” moult, and with the rest of the moult being so extensive it wouldn't be too surprising if it had also moulted a tail feather.


Jenni & Winkler in Moult and Ageing of European Passerines give a range of greater covert moult 0–9, with mean 3.9 and mode 3 for 1,103 Song Thrushes studied; they note that two tertials were moulted in 0.2% of 764 birds, and that no birds of 755 were found to have renewed any tail feathers. However, they do then reference several sources stating that “In England, 1[c]y with all GC and some R moulted were found exceptionally”.

The second bird was not so interesting — they undergo a complete post-juvenile moult, so what is there to look at?! — but was quite unexpected: a Skylark. Not something that's caught often down here, and even less so in the lighthouse garden. The iris was a rich brown; the two non-adult birds (and indeed the two juveniles) I've handled previously had grey-green irides. That might be age related, but without further study with known age birds there's not really a lot else we can say.


Birding was quiet but still pleasant, with a 2cy Red Kite, two Peregrines, and several Ravens passing over the obs. Joe and I took a wander late in the morning, with highlights being a couple of smart Wheatears and, nice for me after so long not having seeing any, species like Rock Pipit, Stonechat, and Fulmar.


The harbour held three dark-bellied Brent Geese and some Red-breasted Mergansers.