26th March

Spring passage seems to be taking a while to get back on track after it was derailed at the weekend, with today's pleasantly birdable almost windless and lightly overcast conditions coming up with relatively poor returns on the passerine front. Chiffchaff struggled up to 30 or so at the Bill/Southwell but Wheatear and Blackcap were the only other common migrants managing double figures on the ground; a brief Ring Ouzel was a first for the spring there and 2 lingering Firecrests came out of the woodwork. Overhead passage was equally underwhelming, with the lightest of passages of Meadow Pipits making up the bulk of the numbers. The sea was busier and also came up with bird of the day in the form of an unseasonable Sooty Shearwater through off the Bill; 32 Red-throated Divers, 98 Common Scoter, 6 Sandwich Terns, 2 Arctic Skuas and a Great Northern Diver also through there represented a fair return for late March.

Hobbies like birdwatching are full of esoteric 'little things please little minds' diversions to keep autistic participants out of mischief and something that's occupied this little mind just lately has been the ageing of Wrens. Ever since Rachel Taylor elucidated a novel method for tackling this hitherto troublesome conundrum more than a decade ago we've always taken Wren ageing to be pretty straightforward. However, quite by chance we discovered that Rachel's flight feather pattern feature we'd been relying on wasn't at all well covered in the standard published and online literature: among the ringers' guides, the Identification Atlas of the Continental Birds of Southwestern Europe and Jenni & Winkler do it fullest justice; despite dwelling at length on much trickier criteria Svensson mentions it just briefly without providing a helpful illustration and neither Demongin or the Ottenby Ringers' Digiguide mention it at all. Since it's perfectly visible in a good in-field photo you'd expect it to be mentioned in the field guides but only Britain's Birds gives it proper coverage, with neither the Collins Bird Guide nor the Advanced Bird ID Guide referring to it at all. We're guessing the humble Wren just isn't trendy enough in the way that, for example, Caspian Gulls or American Black Terns are! Anyway, a few photos from our handlings of Wrens in the last month illustrate the salient features (these are all retraps from the Obs garden breeding population so we're 100% certain that their ages are correct!). Basically, young Wrens (born last year) have a nice clean, parallel lining up of the dark bars across the flight feathers...

...whereas in adults (born before last year) these black bars are altogether more higgledy-piggledy - at first glance you might be fooled into thinking they look pretty parallel but closer inspection always  reveals much more unevenness:

Although we'd generally look for ageing clues on an open wing, this is the sort of feature that's actually often easier to gauge when the wing's closed or at most half-open:

This youngster has much reduced black barring but the characteristic pattern is still quite easily discernible © Martin Cade: