Subject: Is it Pale Thrush? (Black-throated Thrush 赤頸鶇) [Print This Page] Author: vivian Time: 8/11/2009 06:48 Subject: Is it Pale Thrush? (Black-throated Thrush 赤頸鶇)
Or is Dark Throated Thrush?
Pui O
7/11/2009
Thx
[ Last edited by Webcreeper at 8/11/2009 08:15 ] Author: wgeoff Time: 8/11/2009 06:56
Do you have any more photos, from the front?
I can't see the third photo, but the bird looks interesting to me. Author: vivian Time: 8/11/2009 07:17
The third one is no good, is OK?
No more other. Author: wgeoff Time: 8/11/2009 07:36
For me, it's a Black-throated Thrush. First HK record.
Anyone confirm?
Where exactly was the bird at Pui O?
[ Last edited by wgeoff at 8/11/2009 07:41 ] Author: tmichael Time: 8/11/2009 07:43
Got to be Black-throated Thrush - everything right on what we can see.
Long anticipated first for HK.
Mike Turnbull
[ Last edited by tmichael at 8/11/2009 07:47 ] Author: kmatthew Time: 8/11/2009 08:09
Yes, a Black-Throated for me too. Great record!! I guess Black-throated Thrush is now considered a seperate species to Turdus ruficollis??
[ Last edited by kmatthew at 8/11/2009 08:21 ] Author: wgeoff Time: 8/11/2009 08:47
It's up to the Gods to decide but British Ornithological Union have separated them into two species, Red-throated and Black-throated.
This bird appears to have some reddish colour on the outer tail feathers, which is more typical of Red-throated according to the books, so I think we'd better wait for some more comments and perhaps some better photos.
Can Vivian give an exact description of the location please, because people are already on their way to Pui O?
[ Last edited by wgeoff at 8/11/2009 09:06 ] Author: vivian Time: 8/11/2009 10:15
Oh! my god!
How can I express my feel Author: wgeoff Time: 8/11/2009 10:38
Best way, just tell us where you saw it at Pui O. Author: 深藍-Owen Time: 8/11/2009 10:56
detail location just passed to the birder in pui o by vivan. Author: wgeoff Time: 8/11/2009 11:03
Yes, OK thanks Vivian Author: lmichael Time: 8/11/2009 19:01
The problem with this bird is that it seems to be an intergrade atrogularis/ruficollis. I have done a quick check on OB and in the Helm Thrushes monograph (Clement & Hathway) and it seems that a fairly typical hybrid shows Black-throated head and breast pattern and Red-throated tail (presumably to do with dominant genes), i.e. like this bird. It seems that any red in the tail indicates hybrid origins.
So, a first for HK but the Records Committee is going to have a tough job on this one as we will have to consider both the record and the taxonomic treatment!
None of this detracts from the finder though - getting good photos and posting a tentative identification of a problematic bird. Well done Vivian - great bird and as Michael T states a long hoped for addition to the Hong Kong list.
Mike Leven Author: tmichael Time: 8/11/2009 19:47
Mike Leven is quite right, of course, about the problem in the tail. The red is very noticeable and my specific (or sub-specific) reference to Black-throated, rather than Dark-throated Thrush was based on too hasty and bleary-eyed a look at p 279 of the Collins Bird Guide (1st ed.) this morning.
Mike Turnbull Author: wgeoff Time: 8/11/2009 21:58
I am confused. If hybrids can occur, then how can you accept that Red-throated and Black-throated Thrush are separate species?
Can somebody explain what are the criteria for separating species?
Anyway, well done, Vivian, a great find. It keeps us all excited that we can do the same. Author: tmichael Time: 8/11/2009 22:52
Hybridisation does not preclude taxa being considered "species", otherwise we'd virtually just have one species of duck, one of goose etc, etc.
However, it certainly doesn't strengthen the case for treatment of similar taxa as species, at least not under the Biological Species Concept.
However, again, "species" is just that, a "concept", a human construct - there's no "truth" about it, it's just a choice you make about how to regard different taxa.
These two certainly look different, and I believe have some different habitat preferences, so time for me, I think, to listen to the songs and see what I personally think. Brazil (B of E Asia) suggests they sound quite different (but clearly not critically different enough to prove totally unattractive to the opposite sex of the other form, at least occasionally).
Mike Turnbull Author: vivian Time: 8/11/2009 23:30
As Michael T says, 'species' is essentially a human construct. With evolution being a constant process (more or less) at any one point in time there are bound to be taxa where, no matter what definition of species we use, it is very hard to define whether a taxon is a distinct 'species' or a well-marked 'sub-species'. The Red and Black-throated Thrush complex is one of these and whether it has been treated as one or two species has followed fashion to some extent: two species in the 'splitting' C19, one species in the 'lumping' C20 and perhaps two again in the 'splitting' C21.
In determining what is a species we are looking for isolating factors: geographical distribution, habitat, behaviour (song and display) and morphological features which serve to reduce gene flow to a point where genetic lineages remain distinct from each other. In the case of these thrushes it appears (from the literature) that there are some differences in geographical range, some differences in habitat preferences, some differences in vocalisation, and (obviously) some very marked morphological differences. However, the literature (e.g. HBW) suggests that in some areas a high proportion of birds are hybrids, so these isolating factors are, apparently, incomplete. Is the frequency of hybridisation high enough to suggest that mate selection is random (in which case we are probably dealing with subspecies) or is there evidence that it is selective, in which case treatment as two species may be appropriate. From my reading of the literature there is little consensus on this point and hence I am slightly surprised that the usually taxonomically conservative BOU has recently taken the decision to recognise two species.
Mike Leven Author: wgeoff Time: 9/11/2009 16:36
Thanks Mike, very interesting.
The features you mention are those that we humans might use to differentiate species. Has anyone done research on what features a bird might use to differentiate species that would not be obvious to us? e.g. smell, ultra-violet light patterns, ultra-sound or maybe some other sensations we are not aware of?
Is DNA differentiation a more precise tool, or does it just complicate matters?
[ Last edited by wgeoff at 9/11/2009 16:49 ] Author: gary Time: 9/11/2009 22:02
Hi Geoff,
I think further causal discussion on this forum still cannot satisfy your curiosity.
May I suggest 2 references for you:
1.) Handbook of the Bird of the World Vol. 4: Foreword on species concepts and species limits in ornithology by Jürgen H. Haffer.
2.) Speciation in Birds by Trevor Price
I think some serious birdwatchers have the first and the HKU library collection has the second.
Useful link to the first photos by the finder. Note how the spotting on the flanks is quite reddish in tone; another hybrid feature.
Mike Leven Author: ajohn Time: 17/11/2009 13:57
To further complicate the issue, I think the mottling/spotting on the flanks (shown well on one of the photos on the Shenzhen site) seems too well defined for either Black-throated or Red-throated Thrush. I wonder whether this indicates that the bird could be a hybrid between Black-throated and Naumann's Thrush (often considered a subspecies of Dusky Thrush, and previously recorded in HK).
There is a discussion of a probably hybrid Red-throated x Naumann's on the Birds Korea website: http://www.birdskorea.org/Birds/ ... /BK-ID-Thrush.shtml
It would surely be useful to see more photos of the Pui O bird if these are available, especially if these show well the extent of streaking/mottling on the underparts and the pattern of the undertail coverts.
What on first sight appeared to be a fairly straight-forward addition to the HK list is starting to look very complicated for the Records Committee! Author: wgeoff Time: 19/11/2009 15:59
Unfortunately there are no more photos of this bird. I am helping Vivian Cheung, the finder, to prepare a URF for this record and this will be sent in shortly.
Another Dark-throated Thrush was seen on Po Toi today (not by me unfortunately) and this time there are many very good photos by eling. Once again, it appears to be a hybrid Black/Red-throated, although this time a first winter female I think. Author: vivian Time: 1/12/2009 21:57
thanks Geoff
You're so helpful
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Great record!! I guess Black-throated Thrush is now considered a seperate species to Turdus ruficollis??
