I was fortunate to come across another yellow colour form or yellow morph of the Pin-tailed Parrotfinch (Erythrura prasina prasina) (above, below). The last time I saw one of these was on 2nd August 2017 when I observed a single adult male.
Today I saw 5 birds feeding together on bamboo seeds. Two were typical adult males (one shown below, 2 typical females and 1 yellow morph female. Unlike the male yellow morph that has yellow on the beast and rump, the female ‘version’ has yellow only on the rump with a shorter tail.
One of the other females was also a little odd in plumage with some yellow and blue on the wings/back (see below) – I suspect this is a moult.
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: http://www.finchinfo.com/birds/finches/species/pin_tailed_parrot_finch.php
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: http://www.australianfinchsociety.co.uk/article2.htm
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 no 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 …”
Amar-Singh HSS (Dato’ Dr)
Ipoh, Perak, Malaysia
Location: Kledang-Sayong Forest Reserve, Ipoh, Perak, Malaysia
Habitat: Broken-trail along primary jungle
Date: 14th November 2018
Equipment: Nikon D500 SLR with Tamron SP 150-600mm f/5-6.3 Di VC USD, handheld