Join for FREE
It only takes a minute!
Magnifying the passion for nature. Zeiss Victory Harpia 95. New!

Welcome to BirdForum.
BirdForum is the net's largest birding community, dedicated to wild birds and birding, and is absolutely FREE! You are most welcome to register for an account, which allows you to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply
 
Thread Tools Rating: Thread Rating: 1 votes, 5.00 average.
Old Sunday 28th November 2010, 14:10   #1
tomjenner
Forum Member
 
tomjenner's Avatar

 
Join Date: Apr 2004
Location: Hangzhou, China
Posts: 1,233
Help needed with Yellow Wagtail subspecies - Sudan

On Friday morning I visited the newly opened Fenti Golf Course on the edge of Khartoum for some birding. There were lots of Yellow Wagtails of many different subspecies and I tried to photograph as many as possible. I tried my best to identify them, but I have little previous experience with these forms and I would welcome some comments. I posted them on my Birding Sudan blog (link below), so rather than try to upload them all here, I was hoping that you might be able to follow the link and see them there.
Thanks

Tom
tomjenner is offline  
Reply With Quote
Old Sunday 28th November 2010, 19:03   #2
CPBell
Registered User

 
Join Date: Apr 2010
Location: London
Posts: 272
Quote:
Originally Posted by tomjenner View Post
On Friday morning I visited the newly opened Fenti Golf Course on the edge of Khartoum for some birding. There were lots of Yellow Wagtails of many different subspecies and I tried to photograph as many as possible. I tried my best to identify them, but I have little previous experience with these forms and I would welcome some comments. I posted them on my Birding Sudan blog (link below), so rather than try to upload them all here, I was hoping that you might be able to follow the link and see them there.
Thanks

Tom
Tom

The first thing you need to be aware of is that since about the 1960s subspecies have been used as little more than a convention, and are not taken very seriously by taxonomists. When mathematical methods started to be used to classify organisms objectively, it was found that members of different subspecies didn’t cluster together, suggesting that they were largely an invention of the imagination of earlier taxonomists. Genetical studies bear this out. The latest work on Yellow Wagtails suggests that they cluster into three groups: Western, North Asian and South Asian, with little difference among the subspecies within these groups.

Because of this, no changes have been made to the subspecies classification since the 1950s, when Charles Vaurie defined the 18 subspecies that have been used ever since. Most of these refer to plumage combinations that are prevalent within substantial stretches of the breeding range, but variants are common everywhere, and it is pretty futile to speculate on their origin. Typical specimens are quite useful however, especially when trying to work out the origin of birds seen in the wintering area. I describe how in this video – the yellow wagtail bit starts at about 5 minutes in.

So far as your photos go, the first one looks to be a quite pale M.f.beema, tending towards M.f.leucocephala, and the second a typical M.f.feldegg. The third one (and probably number 8) is M.f.lutea. ‘Perconfusus’ was a name that used to be given to birds with blue heads and yellow eye stripes found in the wintering area, in the belief that they had a mysterious Asian breeding area. Later on they were dismissed as hybrids between M.f.flava and M.f.flavissima or M.f.lutea, though even this is quite speculative.

4, 5 and 8 certainly look pretty much like M.f.thunbergi. It will be interesting to see if these disappear as the winter progresses, as the wintering range of thunbergi is much further south. I would be less sure about the one in 6 and 7, however, which looks to me more like a slightly aberrant M.f.feldegg or M.f.melanogrisea. It has a whacking great beak, which is characteristic of these southern subspecies (good for catching grasshoppers), while M.f.thunbergi typically has a short, spiky bill (good for caterpillars) like the one in photo number 8.
CPBell is offline  
Reply With Quote
Old Tuesday 30th November 2010, 16:28   #3
tomjenner
Forum Member
 
tomjenner's Avatar

 
Join Date: Apr 2004
Location: Hangzhou, China
Posts: 1,233
Thanks for the information Christopher. I really enjoyed the video and I look forward to watching some of your others. I also followed the link to your website and saw that you have lots of interesting articles that include the detail about your work with Yellow wagtails and theory of migration patterns. When I have time I will be back for a more detailed read.

Tom
tomjenner is offline  
Reply With Quote
Old Thursday 2nd December 2010, 10:59   #4
CPBell
Registered User

 
Join Date: Apr 2010
Location: London
Posts: 272
Quote:
Originally Posted by tomjenner View Post
Thanks for the information Christopher. I really enjoyed the video and I look forward to watching some of your others. I also followed the link to your website and saw that you have lots of interesting articles that include the detail about your work with Yellow wagtails and theory of migration patterns. When I have time I will be back for a more detailed read.

Tom
Glad you enjoyed the video! I’m hoping to add more in due course, including one describing the Nigerian fieldwork on Yellow Wagtails. I would urge you to keep a log of the proportions of different subspecies you see over the course of the winter, as this would add significantly to what we know about the migratory schedule of the species. It’s one of the few where observations can determine which populations are present/moving through, and I’m not aware of any other published observations from Khartoum, or indeed Sudan in general.

I should probably also add that since some authorities split off Eastern Yellow Wagtail as M. tschutschensis, birdwatchers have started to get very excited about anything resembling the eastern populations that turns up in autumn in western Europe. In the post-war period there was a similar focus on birds resembling M.f.beema, but this faded when it was realised that a lot of ‘beema-like’ birds had a habit of turning up in areas where M.f.flava and flavissima appeared to be interbreeding.

So far as ‘eastern-type’ yellow wagtails are concerned, it needs to be borne in mind that there is a hybrid/intergradation zone running across Fennoscandia between M.f.flava and M.f.thunbergi where all kinds of odd-looking birds turn up. This might be the most likely source of eastern-looking birds, but the only way to really tell is to sample the DNA, which is the reason the split happened in the first place.
CPBell is offline  
Reply With Quote
Old Friday 3rd December 2010, 13:06   #5
MacNara
Registered User
 
MacNara's Avatar

 
Join Date: May 2005
Location: Nara, Japan
Posts: 2,053
CP Bell:

I also looked at your videos about migration, though I haven't gone farther into your website yet.

As far as I could see, you were explaining the differing migration patterns by conditions in the wintering areas only, and taking the summer area and breeding location as a (genetic? historical?) given - 'the birds who breed farther north do such and such...'. But surely an explanation of the migration patterns would have to take account of the conditions at each end of the route, and the conditions in the middle also?

For example, right at the end of video 2, you talk about the Bar-tailed Godwits. The east African bunch go to the place where their European cousins have stayed and fattened up in the winter/spring to fatten up in mid-spring after having used their African reserves of fat to get to Belgium (or wherever).

Why don't they just stay in Belgium and breed there? Or find a nice spot en route between Africa and Belgium where they can breed? Or go to the same place as their Belgian cousins to breed rather than overflying them?

In short, how would this pattern ever have developed - I mean the pattern where two fattening periods were required?

And why would the birds who go farther think that going farther was likely to get them better conditions (given that they are using a lot of their reserves to get there)?
__________________
Animals, birds, people: http://kenyaview.earthworldview.com
MacNara is offline  
Reply With Quote

BF Supporter 2011 2012 2013 Support BirdForum With A Donation

Old Saturday 4th December 2010, 15:49   #6
CPBell
Registered User

 
Join Date: Apr 2010
Location: London
Posts: 272
MacNara

Good set of questions! I’ll do my best to answer them in an accessible way.

Firstly, it’s not strictly true that the scheme I describe in the video takes no account of conditions on the breeding grounds. Actually, this is critical, since the whole thing is driven by the optimal time of arrival on the breeding grounds after spring migration, which varies from one breeding area to another. It’s therefore the later optimal arrival time on the Taimyr Peninsula compared to the Kola Peninsula that determines the different wintering grounds used by their respective Godwit populations.

Your main question, however, is one frequently asked and seldom answered, which is ‘why don’t migrants stay and breed in their wintering grounds or somewhere along the migration route?’ The answer is probably that they do, but they don’t breed sufficiently successfully to establish populations. At the present time, the place where Bar-tailed Godwits breed most successfully is the low arctic. That’s not to say that they couldn’t breed elsewhere, but the populations that breed there are so successful that they expand to fill all of the available wintering sites. Populations breeding less prolifically elsewhere would be driven to extinction by competition from these populations, which is why they don’t stop to breed in Belgium (actually Waddensee, Netherlands).

This is also why west African winterers don’t stop on the Kola Peninsula. Because they would get there significantly later, they would breed less successfully, and so their offspring would dwindle to zero as a proportion of the local population. In technical terms, wintering in west Africa is not an evolutionarily stable strategy for birds breeding on the Kola Peninsula.
Overall, migration strategies develop simply because the birds that use them are more successful than birds that use alternative strategies. If you’re interested in pursuing this further, I’ve set out these ideas in a couple of papers downloadable here (u & y), though I should probably add that they’re technical.

http://www.cpbell.co.uk
http://www.youtube.com/CultoftheAmateur
CPBell is offline  
Reply With Quote
Advertisement
Reply


Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Yellow Wagtail subspecies Cyprus SJC Bird Identification Q&A 2 Monday 28th June 2010 14:10
Yellow Wagtail subspecies, Denmark Terry Townshend Bird Identification Q&A 3 Monday 24th May 2010 14:58
Yellow Wagtail - subspecies ID - Romania Cristian Mihai Bird Identification Q&A 6 Saturday 2nd May 2009 19:06
Yellow Wagtail subspecies identification SJC Bird Identification Q&A 17 Saturday 5th April 2008 07:41
Yellow Wagtail Subspecies Lancey Bird Identification Q&A 5 Friday 1st April 2005 20:28

{googleads}

Fatbirder's Top 1000 Birding Websites

Help support BirdForum

Page generated in 0.14217401 seconds with 15 queries
All times are GMT. The time now is 06:54.