Early May I spent a week on the lovely island of Sardinia. I was of course keen to see Balearic Shrike, the endemic west Mediterranean island ssp (badius) of the Woodchat Shrike.
Now I'm learning by thinking out loud here, so comments are welcome.
The most important difference with the other 3 ssp. is - of course - the (near) lack of a visible white primary patch: about 2/3 of all birds have no white patch at all when perched, 1/3 shows a limited amount on the inner primaries only.
I think visible is a key word here. But first things first.
Here are some pics of the nominate ssp. senator, the default taxon in most parts of Europe. Note the obvious white patch on the primaries.
Woodchat Shrike ssp. senator, 2nd cy female, Rhodopi Mountains, Bulgaria, May 2009
Woodchat Shrike ssp. senator, 2nd cy male, Lesvos, Greece, May 2012 (note the large mask; aged i.e. by the brown juvenile lesser coverts)
Woodchat Shrike ssp. senator, 2nd cy (the unmoulted primary coverts give away this bird's age), Lesvos, Greece, May 2012
Other subtle differences include the colour of the cap (more orange red instead of chestnut in badius), the - on average - darker wing (due to narrower white fringes on the coverts) and the size of the black mask (smaller in badius) and bill (larger in badius). For ID details see Small & Walbridge (2005) or this summary on Surfbirds.
Woodchat Shrike ssp. senator, adult male, Sardinia, Italy, May 2018 (note the funky little detail in the outer tail feather!)
The first Woodchat Shrike I saw on Sardinia seemed to lack a white primary patch. Even though the cap was rather chestnut, the mask on the forehead wasn't very broad and the bill didn't look smallish. With what I saw, combined with the location, I thought I had a full bingo card. But I made the call too early!
When it took off (ok, I came too close), this is what I captured:
That's not a little white I missed, that's a massive wing bar! In hindsight the wing patch must have been obscured: 'overlaying' secondaries sometimes cause confusion.
So this bird was a migrating senator (ok, technically the Iberian ssp. rutilans could not be excluded) instead of the desired Balearic Shrike.
A few more Woodchats were present on the beautiful Capo Ferrato, like this 2nd cy male. The mask is small. The bill: not very deep perhaps, but the cap is orange red.
But look at the outer primaries. Though somewhat faint, there's still a fairly large amount of white visible. Another senator in disguise in badius territory that on a larger distance perhaps could have been misidentified!
And then there was this adult female. There's no white wing patch and the bill looks quite heavy. There are hardly any pale fringes on the coverts. All looked good for badius!
Then it took off. Hey, perhaps it's not that much, but there's certainly more white visible on the base of the primaries than I expected!
So is this acceptable for badius in flight? Well, I guess so...
I saw this individual on 3 days, from many angles and I never saw a wing patch when it was perched. Apparently the white is shorter than the primary coverts (and was therefore obscured when perched).
Boy, it's annoying that our national museum of natural history is closed for renovation for 2 yrs. I'd love to lift some primary coverts on badius, to see what's underneath.
In any case it was obvious that even within its range, a careful look was still needed to ID Balearic Shrike.