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A note on the white spot on the diving duck's chin

Posted by deheeg VIP ,

A black spot in our knowledge about the relationship of diving ducks?

Personal observations show that adult males of a number of diving ducks (genus Aythya) show a white spot under their chin, just at the base of their bill. Although not much is written about these spots in literature, museum skins show the same white spots in the same species. Canvasback, common pochard, ferruginous duck, Baer's pochard and Australian white-eyed pochard show this spot, to name a few. Other closely related ducks such as redhead, tufted duck, ring-necked duck and Madagascar pochard do not show this spot. 

 

As this intrigues me, next questions came to my mind are:

  • Can the presence (or absence) of the white spot be lead back to only one Aythya-species?
  • If yes, how did it end up in the other species?   
  • Is there a correlation between the morphologic character and the genetic relationship between species within the genus of Aythya

Does anyone know more about this topic and can you recommend sources to me?

Please let me know. 

 

From my personal observations/ skin studies: 

 

White-eyed pochards

Ferruginous duck

Aythya nyroca

Baer's pochard

Aythya baeri

Australian white-eyed pochard

Aythya australis

Madagascar pochard

Aythya innotata

White spot

White spot

White spot

No white spot

  

Red-headed pochards

Common pochard

Aythya ferina

Canvasback

Aythya valisineria

Redhead

Aythya americana

White spot

White spot

No white spot

 

I have no valid data yet on the white spot in scaups (Aythya novaeseelandiae, Aythya affinisAythya marila), and the closely related tufted duck (Aythya fuligula) and ring-necked duck (Aythya collaris). 

 

baer1.jpg

Above: male Baer's pochard (Aythya baeri) shows the white spot on its chin. 

Specimen photographed at Natural History Museum at Tring, UK (Harteman, 2019). 

 

madagascarpochard.jpg

Above: these two males Madagascar pochard (Aythya innotata) do not show the white spot on their chin. 
Specimens photographed at Natural History Museum at Tring, UK (Harteman, 2019). 

 

common_pochard_and_redhead.jpg

Above: Redhead (Aythya americana) at top and common pochard (Aythya ferina) at bottom. 
The redhead does not show the white spot, but the common pochard does.

Canvasbacks show the spot as well. 

Specimens photographed at Natural History Museum at Tring, UK (Harteman, 2019). 

 

ferruginous_and_baers.jpg

Above: Baer's pochard (Aythya baeri) at top and ferruginous duck (Aythya nyroca) at bottom; both show the white spot. 

Specimens photographed at Natural History Museum at Tring, UK (Harteman, 2019). 

 

Direct link: https://www.harteman.nl/pages/aythya 

 


 
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