The Strange Case of the Tit in the Daytime

Regular sufferers of Imperfect and Tense are probably due a bit of serious nature news. Think of it as time off for good behaviour. Yours, not mine.

At Hanson Environmental Study Centre (HESC), there's recently been a bit of a kerfuffle over bird ID, in particular regarding the separation of the similarly-sized Marsh and Willow Tit. These two species are very alike and, in the absence of a qualified bird ringer and all their mist netting paraphernalia, are best identified by call.

Reading Birds Britannica by Mark Cocker and Richard Mabey, I was amazed to discover that the Willow Tit was not recognised as a separate British species until 1900. This followed some clever detective work by two German ornithologists in 1897, who discovered a couple of mis-identified Marsh Tit skins in a tray at the British Museum. What a day that must have been.

The Willow Tit, Parus montanus, has grey-brown plumage above and off white plumage below. It has a black cap, a black bib and white panels on the sides of the head. Just like a Marsh Tit, Parus palustris. To be fair, it's reckoned that if you had a specimen of each side by side, the Willow would have a more pronounced bull neck, making it like a 'stretched limo' version of the Marsh.

For the last century, it has been thought that the most obvious difference, and I use the word 'obvious' advisedly, is the presence on the Willow of a pale panel on the secondaries of the folded wing. But as Willows can lose this in summer through abrasion and a newly-moulted Marsh could have a suggestion of a pale panel, it's not a definitive distinction. In the Willow, the dark crown is supposed to be dull, whereas in the Marsh, it is glossy. However with changing light conditions, that's never going to be an easy call. My thanks to the Collins Bird Guide (Britain and Europe) for those few facts.

Should anyone care about this, apart from the hordes of pedantic, obsessive birders who fret over stuff like this all the time? Well, both birds are on the British Red Data List and the reasons for their decline are not fully understood. Without that understanding, it is difficult to know which habitat management techniques to deploy to prevent further loss of numbers and the real threat of extinction of these species within these shores.

And so to their calls. Until relatively recently, this was the best diagnostic tool available to split the two species. The Marsh Tit has a distinctive 'pitchoo' call (scroll down here, click and listen), whilst the Willow Tit has a 'zi-zi taah taah taah' call (scroll down here, click and listen).

Easy, eh? But what happens if neither of them are calling? In the last few years, it has been realised that the Marsh Tit has a small white patch at the base of its bill. This is absent in the Willow Tit. The only trouble is, neither species is very good at sitting still and carefully angling its head so that you can have a jolly good look.

Have I mentioned that of the two, Willow Tit is more likely to be found near water? Or that Marsh Tit inhabits broad-leaved woods. Honestly, it's enough to make Miss Marple throw in the towel and take up pole dancing.

On Saturday, whilst the light was great, The Admiral and I ventured down to HESC and found ourselves in the Woodland Hide in the company of The Singer (**new character alert**). We all sat, watching three black-capped tits visiting the feeders and tried to figure out whether we had three Marsh, or two Marsh and a Willow. I hadn't taken along my camera, which was a shame because, as I said, the light was great. None of the birds were calling, but one did seem to have a larger head.

On Sunday afternoon, The Admiral and I returned, camera'd to the eyeballs, to be greeted by swirling fog and two black-capped tits, either two Marsh or one of each. I did manage to capture one image of a Marsh, but as the light was poor, it was nothing to write home about. A bird, sounding not unlike a Willow Tit, was calling, but whether it was one of the two birds we were looking at was another matter.

Definitely, absolutely, positively a Marsh Tit, I think!

Today I discovered that help was at hand in the shape of LGR Evans, self professed birding expert of the UK and presumed permit holder of HESC. A recent blogpost of his at Buckinghamshire Birding contains further insights into this particular avian conundrum.

I am left with the odd feeling that on Saturday we saw but did not hear a Willow Tit, whilst on Sunday we heard but did not see a Willow Tit. Everything else was Marsh.

To be continued...