I had a quiet morning bird watching on 4th November 2022 at Ipoh, Perak. But when I came out of the forest there was a large mixed-feeding group of swifts. More than 40 birds together, comprising:
Grey-rumped Treeswifts (Hemiprocne longipennis) 15
Silver-rumped Needletail/Spinetails (Rhaphidura leucopygialis) 10
Plume-toed Swiftlets (Collocalia affinis) 10
Other unidentified Swifts 5-10
Wells (1999) notes that Grey-rumped Treeswifts foraging groups may be from 5-50 birds.
Some of the swifts, with scaly breasts, I did not initially recognise until I processed the images.
See these two birds below.


They are juvenile (possibly male) Grey-rumped Treeswifts. I have not seen juveniles in flight prior to this.
The next two images are of adults (male and female).


References:
Wells, D.R. (1999). The birds of the Thai-Malay Peninsula: Vol. 1 (Passerines). Christopher Helm, London
Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
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Vanessa Lim
Hah! What an obscene and hilarious scientific name!
BESG
Dear Vanessa,
Thank you for your humour. The longipennis refers to the long wing feathers which criss-cross each other at the back of the bird.