domingo, 19 de enero de 2014

A 'Black' White Stork at Aiguamolls, Girona

A dark, blackish stork was videotaped using hand-held digiscoping techniques on 10th January 2014 (Sergi Sales, Carolina García, Ricard Gutiérrez, see below). The bird resembled initially a Black Stork Ciconia nigra but obviously it was not because of entirely dark feathering. The possibility of a melanistic bird arose, but caution with these plumage aberrations is needed and indeed a paper on this species apparent cases of melanism was published not many years ago (Gordinho, L. 2008 Â propos des Cigognes blanches Ciconia ciconia 'melàniques' Ornithos 15: 304-307).





Investigating through the net, and commenting the record with the fellows from the Empordà area, it became clear that there was not only one black (the above bird) but three 'dirty' storks in different degree of darkness (Àlex Ollé in litt).

In fact, the portal ornitho.cat gathers sightings of these birds since at least November 2013 (links to ornitho.cat pages under the date, all photos and info from that site and credit to their authors):

- 3.11.2013 Joan Ventura sees one dirty bird at Mas Trencat, Castelló d'Empúries and comments: Sembla que no és una cigonya negre sn una blanca que per algún motiu està tacada de negra.[It seems that it is not a Black Stork but a White Stork that, for some reason is stained black]

© Joan Ventura at ornitho.cat

- 4.11.2013 Marc Rovira quotes 1-2 ind at Aguait Quim Franch, Castelló d'Empúries / Castelló d'Empúries 'with black feathering'.

- 9.11.2013 Pere Baucells  Colomer quotes one bird well black and suggests if it was covered by any kind of black dye Un individu ben negre. Untada d'algún tint negre???

© Pere Baucells at ornitho.cat
 
© Pere Baucells at ornitho.cat

 - 11.11.2013 Joan Ventura quotes that TWO dark birds remain at the Aiguamolls area within a grand total of 230 individuals.

- 19.11.2013 Marc Rovira sees one dark bird within a group of 44 individuals at Arrossars de la Gallinera, Castelló d'Empúries.

- 23.11.2013 Jordi Faus comments that at El Cortalet area, Aiguamolls de l'Empordà, there were one very dark bird and another greyish individual: N'hi havia una de ben negra i una altra grisosa

- 4.1.2014 Pau Barnés and Jozef Leestmans quote 120-156 individuals at Estanys d'Europa and introduce one image of the 'greyish bird'.


© Pau Barnés at ornitho.cat
- 10.1.2014 Video above
- 11.1.2014 Miquel Arxer quotes one very dark bird at Aiguait Quim Franch, from Aiguamolls.
- 18.1.2014 Jozef Leestmans recalls two birds again which he quotes as '1 Completely Black - Melanistic one partial melanistic looked dark grey'

© Jozef Leestmans at ornitho.cat
Finally, Àlex Ollé, on 19.1.2014 comments as follows regarding the three stained storks and confirms that there were up to three birds:

"...n'hi han hagut fins a 3, tot i que sembla que ara mateix s'observen dos, una de molt negre i una de 'gris' (com la foto que t'adjunto). De les tres, una encara hi és i és molt fosca, una altra un xic més apagada amb anella, que crec que ja no s'observa, i una que simplement està tacadeta. Ara bé, l'ocell que tenia anella, aquesta era hexagonal, negre i amb els dígits blancs; del tipus centreuropea (alemana, danesa,...). Amb tot, no vaig poder llegir-la, ja que també estava tacada. Almenys una de les cigonyes "negres", s'ha vist repetides vegades a l'abocador, com totes les cigonyes del PNAE, pel que podria ser el punt d'orígen del tema. "

'There have been up to three, although (on January 2014) there seem to remain two, one very black and another grey (like the below photo). Of the three, one -the black one- is still around while there is another greyer which carries a ring, that I think it has left the area, and another simply a bit stained. It's worth noting that the ringed stained stork was carrying an hexagonal ring, black with white digits, such as those used in central Europe (german, danish...). Unfortunately I could not read the ring since it was stained too. Al least one of the 'black' storks has been seen repeatedly in the county dump, as all Aiguamolls Park Storks, so the dump could be after the origin of the whole thing'.

Incidentally in the photo that Àlex encloses the third stained stork is also visible along white 'regular' ones, the grey and a Common Crane (Grus grus).

© Àlex Ollé. Note the greyish bird (background to the left and a mid-stained bird in the lower left front. Aiguamolls de l'Empordà, Autumn 2013.

 Are these birds melanistic or have a plumage aberration?

It is worth having a look to the good work of van Grouw, H 2006. Not every white bird is an albino: sense and nonsense about colour aberrations in birds. Dutch Birding 28: 79-89. Plumage aberrations have to be named carefully and, as Gordinho 2008 states, particularly in the case of White Storks.

Gordinho (2008) analyzes and discusses four cases of claimed 'melanistic' White Storks: two from Portugal, one from Hungary and one from Morocco.  The two from Portugal were demonstrated to be oiled birds as were others from Oman also reviewed. Contacted regarding the Aiguamolls darkest bird and prior to know there were actually three in different degrees of grey shade, Gordinho (in litt) commented that even in the darkest bird

 'I see some contrast between the feathers that should be black (remiges, greater coverts, eye stripe) and the feathers that should be white. Also dropping wings, scruffy vent, retracted neck... Based on this one out-of-focus image [an image I provided of similar quality as the video, note of the editor], looks like a good candidate for a stained bird'.

Indeed in his 2008 paper he concludes that  'when confronted with an abnormally plumaged bird, birdwatchers are urged to take a full description covering the bird's structure, carriage and behaviour'. As it has happened in this Aiguamolls case, he states 'discussing the record with locals, even if not birdwatchers, may prove equally important to determine the causes of abnormal colouring'.

Black colour causes an illusion of a certain subtle change of structure and shape as it can even be seen in the below image of the dark stork in flight compared with 'regular ' White Storks

© Àlex Ollé, autumn 2013 Aiguamolls de l'Empordà, Girona


It seems clear that, paraphrasing the van Grouw paper title, not every white bird is an albino, nor every dark bird is a melanistic individual!.



Acknowledgements

Thanks to Àlex Ollé for his input and photographs plus Luis Gordinho for his paper at Ornithos and opinion on the darkest bird at Aiguamolls de l'Empordà.


1 comentario:

Merand Vincent dijo...

A picture I shot on 2013 Feb 2nd at Aiguamolls...
http://vincent3m.info/cigo.html#cigo