Sunday, 27 March 2022

In the Absence of Pink

A family day with small granddaughters has meant birding within buggy-pushing range, so at least the local Yellow-browed Warbler got a quick visit. After that it was all down to the garden. Thanks to an afternoon heads-up from Mike Morse in Bridport, I was suitably alert when this flew over...

Third garden Red Kite of the year

And so to the main topic of this post: littoralis Rock Pipits...

In THIS post (dated 9th March) I wrote:

'...I've given myself a modest local challenge: find a spring migrant littoralis (so-called Scandinavian) Rock Pipit among the resident petrosus birds.'

My idea was that this would involve finding a littoralis in summer plumage, i.e. with pinky flush to throat and upper breast, much grey on the head, and diminished breast streaking. So far I have failed to do that. However, I do seem to have found a few 'probables', and I get the impression one or two NQS readers think so too.

But 'probable' littoralis is no good at all. 'Probable' is one of the worst words in birding. Any bird saddled with it might as well not have bothered showing up at all. Understandably, I want a 'definite' littoralis. But surely there's no way that can be done without pinkness? Well...

A littoralis Rock Pipit's summery glow is attained through its pre-breeding moult. Pipits & Wagtails by Alström et al* has some interesting stuff to say about the pre-breeding moult of Rock Pipits (which largely takes place January to March):

'In littoralis on the Swedish west coast most individuals moult at least 50% of the head and body feathers (mainly crown, mantle and breast). These birds frequently also renew 1-3 pairs of tertials and the central pair of tail feathers, and occasionally a few median and inner greater coverts.'

'The moult of petrosus is either absent or limited to a few feathers on the crown, mantle and lower throat/upper breast...'

Although the authors don't state how many petrosus they examined, they came across just one which had renewed any wing or tail feathers at all (the central pair of tertails) in its pre-breeding moult. In other words, a spring petrosus Rock Pipit is very unlikely to have new tertials or central tail feathers. To put it another way, any spring Rock Pipit which does have new tertails and/or central tail feathers is almost certainly going to be littoralis, and likely this will be evident in extensive head and body moult too. Which brings me to Rock Pipit #10.

I first came across Rock Pipit #10 on 15th March, then again on 20th. Here is a collage of those two encounters. Note the yellow arrows...

Rockit #10

The top two shots show five days of growth in the central left tertial, and the bottom two highlight the central tail feathers and central right tertial. All moulted and in active growth. This bird is undoubtedly NOT petrosus.

In addition to the wing and tail moult, #10 was strikingly pale below. On 20th March it was on a sunlit slope with another Rock Pipit (which did a bunk before I could photograph it) and noticably had much paler underparts...

From a distance this bird positively glowed in the sun

Despite absence of pink, I have absolutely no qualms in calling this a definite littoralis Rock Pipit.

I'll be honest, I had no idea that evidence of pre-breeding moult in wings and tail might be a key factor in separating spring littoralis from petrosus. Clearly it is, and learning this fact has been a game changer for me. I've yet to see any Rockits quite like #10 though, which incidentally has not reappeared since 20th March. I suspect it is in Sweden right now, going pink.


* I am indebted to Kev Thornton for kindly providing access to his copy of Pipits & Wagtails.

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