Dunlin again - what do centralis really look like? (1 Viewer)

[Jane Turner]

Criteria 7 - solidness and tone of belly patch

1. Many broad white tips - much of the shield dappled and rather greyish
2. Few thite tips, shield not deep and sooty toned
3. Sooty shield with some narrow white fringes
4. only very few white edges in solid sooty shield
5. Solid deep black

Patchy belly shields are unlikely on Siberian and Alaskan birds. Very solid dark shields are unlikely on European and Canadian birds


I score yours 3-4 - more 4

 

[Jane Turner]

So in summary birds with your birds combination of features can be found from the centre of centralis range east to the pacific.

 

[Steve Lister]

Just about the most helpful replies I have ever seen on Birdforum - great stuff Jane.

Steve

 

[Jane Turner]

Light is nasty just now, but there are plenty of exotic Dunlin here today - a very long winged white faced bird that has a mega wing bar (but so do most of todays - are they all centralis? Also a nice size comparison with a dunky arctica Also an odd bird with mega bill, loads of pale tips to the scaps but very weak shiled

Tide is coming in so I may get close to compensate for the grotty light.

 

[Jane Turner]

And a few photos of todays white-faced birds. I have video which I may be able to get wing bar details from

 

[robby thai]

Always hoping to learn something but this one is a bit heavy for me.

However I have a question; I recently posted a photo of a Dunlin wintering in Thailand, there is no mention anywhere I can see of any of the subspecies wintering here so which subspecies is it likely to be?

 

[Jane Turner]

Here are some wing bars - inc some def white to the shafts of the inner 4 primaries (which is supposed to be diagnostic for non-European

 

[Jane Turner]

Always hoping to learn something but this one is a bit heavy for me.

However I have a question; I recently posted a photo of a Dunlin wintering in Thailand, there is no mention anywhere I can see of any of the subspecies wintering here so which subspecies is it likely to be?

Most likely to be one of the Pacific Coast races - from Siberia or Alaska

 

[Strandman]

Great thread! in case of interest here's one from the Stour last week (17th May) that I paid a bit of attention to as it had limited black and some broad off-white tips to scaps. But looking at your other criteria, black belly stops at the legs and doesn't extending onto the very sparsely marked vent.

 

[Jane Turner]

The belly patch is a 3 on this scale which is possible on birds from just about anywhere. http://www.birdforum.net/attachment.php?attachmentid=627331&d=1495102310

The white face and scaps are outside the range of European birds and its tempting to say there is white on the inner primaries.

 

[Jane Turner]

Got some better light today - but a lot of disturbance and some nice exotic Dunlin

 

[Jane Turner]

Got a stunning Dunlin today - though it as invariably the furthest away and spent most of its time asleep.

-Rich chestnut scapulars with a line of white-tipped ones.
-Very large "lumpy" looking bird
-Long rather fine bill
-Immense wing bar
-high riding belly patch

 

[Samuel Perfect]

Massive thank you Jane for the effort you put in assessing the Dunlin. Apologies for my late reply.

A few questions. Could you explain what the info in the table you made means in #82? Do the crosses mark the criteria scores which did not fit the description of the bird whilst the gap shows the most likely origin of the bird by process of elimination? Was it not possible to rule out subspecies using shield colour/solidness, rear scap tips, face colour/streaks, upper breast streaking, and flank streaking as there are no crosses in their rows? http://www.birdforum.net/attachment.php?attachmentid=627336&d=1495103160

Could you also attach the scatter graphs for "lower scapular centres" and "solidness tone of belly patch" as post #77 and #81 show the wrong graphs?

I tried IDing a bird attempting to breed on North Ron using your criteria but haven't reached a conclusion. This individual has been singing on the island for the past few weeks and judging from the range maps is likely to be ssp. schinzii. The red dot shows what I scored it for each criteria. Flank streaking=5, upper breast streaking=2, lower scapular tone=2, rear scap tips=2, face ground colour/streaking intensity=2,shield size=2. I have yet to score lower scapular centres and solidness of belly shield and place them on the graph. However, I did struggle judging criteria 3(lower scap tone) and criteria 6 (extent of belly shield). Is the % shield cover measured from the chin to the upper or lower edge of the vent? I'd be keen to know if you score the bird the same as I did as I found judging several of these characters rather difficult.

Pic by Simon Davies, posted with permission.

 

[Jane Turner]

Yes you have it - the gaps are where the bird is more likely to be be from. That N.Ron bird looks like it doesn't have many exclusion features. The belly patch looks European style though and the face isn't white enough for an exotic one especially since its a male

The way I work with the features is to have all 60 odd birds in my data set in rank order and compare the test bird. When I have found more breeding bird photos I'll ask at least someone else to rank them all too. I'll sort out the correct graphs when I'm back on my main PC

 

[Jane Turner]

I'm still mulling over the best way to assess features - belly shield size is a tough one because the really big ones ride high as well as carry on low - here is your bird (which I score as a 2) in a few others. Also the missing scatters

 

[Samuel Perfect]

As soon as I posted, I realised I answered my own question and your post #82 made sense to me, amazing how that happens.

Thank you for sharing the two scatter plots.

I originally took the measurement for the belly shield size incorrectly. Do you select the end of the vent or distal end of the undertail coverts as the lower margin?

The reason I chose the singing North Ron bird is because I wanted to compare a British breeding Dunlin against the scatter plots to see if it fitted within the same range of scales for each criteria of ssp. schinzii. I essentially made the assumption the bird was breeding at 0 degrees longitude and checked the scale for each criteria to see if it fell in the range for the other breeding birds at 0 degrees longitude.

 

[Jane Turner]

UK is a little more than 0 - its offset 7.5degs so Greenland appearrs at 0... but the logic is otherwise bang on!

I'm thinking of changing a little and going for tip of the tail since its easier to locate! All that happens is a minor redefinition of the descriptors - the rank remains the same

 

[skwoolley]

Centralis Dunlin?

Is there any reason why this Dunlin is not of the Siberian form *centralis*? Also comments welcome on this brute of a gull......both last week in Estonia.

 

[lou salomon]

the gull is a subadult GBBG.

 

[SteveClifton]

The gull is a sub-adult Great Black-backed Gull.

Pass on the Dunlin.