domingo, 10 de noviembre de 2013

Presumed hybrid Grey heron x Great White Egret (Ardea cinerea x Egretta alba) in Doñana, Spain

Presumed Ardea cinerea x Egretta alba. Entremuros, PN Doñana, Sevilla, 1.11.2013 © Carlos M.Martín

Versión en castellano: usar 'Translate/Traducción' applet


On the 1st of November 2011, while birdwatching within Doñana Natural Park at Entremuros area, Sevilla, Carlos M.Martín noticed what immediately recalled him an hybrid between Grey Heron (Ardea cinerea) and Great White Egret (Egretta alba). It was close to a pond at 37º06´18.86´´N 6º15´28.32´´O where there were dozens of Great White Egrets, some of them ringed.  He took a photo lucky enough to capture within the same frame (see above) the presumed hybrid (right) and both alleged parent species (Great White Egret, left, and Grey Heron, center).

As he stated in his notes on the observation:

'Baso mi apreciación de que puidera tratarse de un "presunto" híbrido -más alla de un plumaje aberrante- en que presenta caracteres que evocan a ambas especies: el pico amarillo y la cara blanca, así como el diseño del color sobre la narina, en la base del pico, parecen señalar a Garceta Grande, mientras la generalidad del plumaje -y un atisbo de moño- sugiere una "aberrante" coloración de Garza Real'.
 
 'I support my assessment that the bird might be an "alleged" hybrid-beyond any kind of aberrant plumage - in presenting characters that evoke both species: yellow bill and white face and the color design around the nostril, in the bill base, seem to point to Great White Egret, while the generality of plumage, and a hint of bow-suggests an "aberrant" coloured Grey Heron '.

Discussion

The bird clearly had a Grey Heron (hereafter cinerea) 'input' shown in the greyish tinge, shoulder patch and mantle colour, plus neck marks. However, structure (despite a somewhat alert posture in the photo) looks slender than cinerea, then approaching nearby Great White's (alba). Leg length seems also closer to that of alba as well as bill structure, including the lore colour and shape. Besides, bill structure (see below) is not exactly that of alba but it is narrower in the base than that of cinerea (adult depicted, even thicker in some first-calendar year birds). Bill tip is black, as in alba too. 


Photo-collage of Egretta alba (left), adult Ardea cinerea (middle) and presumed hybrid (right) from Carlos M.Martín photo above and wikimedia commons Grey Heron. Notice shapes of bill and bare parts in all three individuals (© Ricard Gutiérrez, the collage).


McCarthy (2006) Handbook of Avian Hybrids of the World  reports natural hybridization in the Netherlands and that the breeding range of both presumed parent species overlaps in South Eurasia. It reports cases in Latvia (Baumanis 1998) and the Netherlands (Eigenhuis 1984), the latter showing some traits similar to the Doñana bird. Kajzer & Rubacha (2010) account for another case in Poland.

Albeit not much reported, cases of hybridization having Grey heron as one of the parents also include not surprisingly the Purple Heron (A.purpurea) (e.g. Campos 1990), as the other but even more surprisingly than the alba case depicted here, the Little Egret (E.garzetta) too (Lippens & Burggraeve 1983). Caution is needed taking apart cases of plumage aberrations when dealing with odd-looking herons such as this one.


References


Citation

Martín, C.M. & Gutiérrez, R. 2013. Presumed hybrid Grey heron x Great White Egret (Ardea cinerea x Egretta alba) in Doñana, Spain. Birds in Spain Blog. Retrieved from http://birdspain.blogspot.com/2013/11/presumed-hybrid-grey-heron-x-great.html