Taiwan: Streamside Birds

I have long had a particular fascination with birds that live along rushing streams (or, these days, that hang around the dams we build to block them).  Life along a torrent poses challenges for birds - in particular, the roar of the waters competes with any sounds the birds make, so signalling others of their kind by voice can be tricky. As a consequence a number of streamside birds have developed combinations of shrill, high-pitched calls and, often, flash-pattern, black-and-white plumage that they show off with tail-wagging or bobbing displays and other stylized movements - with the additional value that this combination of pattern and display can help to conceal the bird from a predator against a background of foam-flecked water. 

I am particularly fond of one group of stream birds, the graceful and elegant forktails (Enicurus). Taiwan is home to one I had never seen, so en route to our next stop, Xitou, we stopped off to have a look for it at a spot where Bob had previously photographed a pair. They weren't there when we arrived, but with a bit of patience and some help from a curious passerby we soon located them.

The Little Forktail (Enicurus scouleri) is the smallest and most compact of the forktails, and if it lacks the slim elegance of some of its cousins it is a charming bird nevertheless. You can see how it's striking pattern breaks up the bird's outline when viewed against the background of the light-dappled water. Notice the pink feet!  On the Asian mainland, this forktail is a bird of high elevations, above the range of the other species; here in Taiwan, where it is the only one, it can be found - as we found it - lower down. 

Forktails are members of the chat/old world flycatcher family. The same family contains other Asian stream birds, and we caught up with two of them once we arrived at Xitou. 

One was an old acquaintance: the Plumbeous Redstart (Phoenicurus fuliginosus affinis), a bird I first met many years ago in the Himalayas and have seen again in mainland China. This is an adult male.  This bird, with a close cousin from Luzon, is usually placed in a separate genus, Rhyacornis, but a recent molecular study of the chats shows that it belongs with the other redstarts – something, by the way, that I proposed myself in a paper that appeared back in 1979.  

It has the distinctive habit of constantly fanning and depressing its tail, something that differentiates it from its cousins but, in my opinion, is simply another example of a streamside bird flash display.

The female Plumbeous Redstart is a very interesting bird. It's plumage is quite different from that of other female redstarts, but looks very much like that of a juvenile. In my old paper I proposed that this was a case of a species that had lost sexual dimorphism (in its closest relatives the male and female are alike), but reacquired it by retaining a modified, greyed out version of its juvenile plumage into adulthood in the female birds.  The female, by the way, has white tail patches that it reveals when it fans its tail feathers.

The other stream bird at Xitou was the Taiwan Whistling Thrush (Myiophoneus insularis), an endemic species.  While ornithologists have concluded that the chats (such as the forktails and the water redstarts) are more closely related to flycatchers than to thrushes, the idea that these big, robust birds are not thrushes seems counter-intuitive.  Nonetheless, the molecular study I referred to earlier shows not only that they are oversize chats, but - even more surprisingly - that their closest relatives are the forktails.  Other than their preference for running water, the two groups of birds seem about as different as can be - but that's what the genes tell us.  Whistling thrushes lack the flash-pattern plumage of forktails, and can seem downright dull - but perhaps they have another way of drawing attention to themselves.

These photos seem to show a completely different bird from the dull-coloured blackish creature above - but it's the same individual, this time taken with a flash.  The result brings out striking structural blues that, I suspect, birders rarely see.

Are these shots unnatural?  Or are they showing us something of the brilliance that other whistling thrushes, who see further into the ultraviolet than we do and have plumage patches of pure ultraviolet that we cannot see at all, see when they encounter one of their own kind? Is that what gives this bird its "flash"?