“I was fortunate today to come across a single male yellow colour form or yellow morph of the Pin-tailed Parrotfinch (Erythrura prasina prasina). This bird was on its own and was feeding actively on bamboo seeds (I saw the red colour forms later at another site). I suspect it may be breeding as it was feeding in a frenzy that lasted 30 minutes non-stop, despite my close presence.
“The bird can look different in different light. In harsh light the yellow on the breast and rump/tail are harder to appreciate and seem to merge with the cinnamon or buffy underparts. In softer light the yellow is clearly seen. It is even called ‘Yellow-bellied Parotfinch’ in some literature despite being the same species.
“Wells (2007) states that the yellow form occurs in a ‘minority’. Payne (2017) in Handbook of the Birds of the World Alive says it is ‘rare’. The Finch Information Centre states that is an ‘autosomal recessive mutation which occurs naturally in 5-8% of the wild populations’ – see LINK.
“Tulk, writing for the Australian Finch Society on Gouldian Finchs and colour variants, contributes to the issue: ‘It is amongst the small number of bird species in which this phenomenon exists (multi-morph). There are many examples of species that have established two colour phases. … The Crimson Finch and the Pintailed Parrot-finch can be used as an example. Both species have red and yellow colour forms or morphs established in the wild. These naturally occurring colour variants show part of the continuing evolutionary process of these species. Colour variants are a naturally occurring phenomenon and can only exist in numbers if they are well established. In the wild, this is difficult, as natural selection is far more random …’ – see LINK.
“Gerhard and Wörz, when discussing the Pin-tailed Parrotfinch, especially from a breeding perspective, offers this information ‘This colour morph does not constitute another subspecies but is a mutation which influences the synthesis of Carotinoides. These birds now longer produce the cantthaxantin responsible for the red color. The mutation can be found in males and females. The only difference between red- and yellow-bellied females is the colour of the rump which is yellow with the mutants. Currently ‘yellows’ are rarer than the red ones and as this mutation is inheriting recessive …’
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
2nd August 2017
Location: Kledang-Sayong Forest Reserve, Ipoh, Perak, Malaysia
Habitat: Broken trail along primary jungle