I met up with a breeding pair of Rufescent Prinias (Prinia rufescens extrema). I noticed that the birds had an indistinct, brownish upper breast band (more prominent in one bird). It was not very obvious and has to be seen in the right posture and lighting. In literature the neck, throat and underparts are whitish with tawny buff at sides of lower breast and flanks (see Wells 2007 & HBW). I have not read about this upper breast buff plumage before. Looking at my older images, it can be seen in some birds in the past in high quality images but not all the time.
I had posted on a similar observation for the Yellow-bellied Prinia (Prinia flaviventris rafflesi) in February 2019; again they were breeding birds (only males).
This is not a stain on the feathers. I suspect it is a breeding change, more prominent in males.
Amar-Singh HSS (Dato’ Dr) – Ipoh, Perak, Malaysia
Location: Ulu-Kinta, Ipoh, Perak, Malaysia
Habitat: Mixed Secondary and Primary Forest
Date: 6th July 2020
Equipment: Equipment: Nikon D500 SLR with Nikon AF-S Nikkor 500mm f/5.6E PF ED VR, handheld with Rode VideoMic Pro Plus Shotgun Microphone