Leucistic Glossy Ibis, an identification pitfall for Sacred Ibis

At c.14:20 hour on 3 October 2022, an alleged Sacred Ibis Threskiornis aethiopicus was seen at La Ràpita, Ebre Delta, Montsià, Catalonia. The species is a rarity in the country, besides having been recently considered as a pest species.

After some search, on 4 October 2022,  Sergi Sales found the ibis which showed a large white body and black neck. However, a careful observation revealed that indeed it was not a Sacred but a leucistic Glossy Ibis (Plegadis falcinellus), a frequent species at Ebre delta numbering c.40.000 birds in autumn 2022 (David Bigas pers.comm.), see @sales_sergi tweet below and his original photo.

 

Aquests dies pel Delta de l'Ebre volta un Capó reial mig leucístic que esta donant mal de cap perquè la distribució del clar/fosc coincideix bastant amb el seu parent, l'Ibis sagrat. Podem comparar a les fotografies totes dues espècies.Realment un ocell ben curiós @FundPlegadis pic.twitter.com/sWvKwf6Enp

— sergi sales🎗 (@sales_sergi) October 12, 2022

 

Leucistic Glossy ibis (Plegadis falcinellus) © Sergi Sales X 2022.

 

 

This is not the first case of a known leucistic glossy ibis e.g here  but this particular bird almost matches the pattern of Sacred Ibis, a frequent species in places such as Italy (see photos below from Po Delta in October 2018). Indeed some growing feathers of ‘true’ Sacreds could mirror in the distance the patchy pattern of the Ebre delta bird. 

 

Threskiornis aethiopicus (&1  Bubulcus ibis). Po Delta, Italy, 18 Oct 2018 (© Ricard Gutiérrez)

Threskiornis aethiopicus (& Phalacrocorax carbo). Po Delta, Italy, 18 Oct 2018 (© Ricard Gutiérrez)

 

A real pitfall demanding a rather close and careful observation, not a simple trust on bird colours and overall shape. 

Thanks to Sergi Sales for sharing the image and uncovering bird’s identity