Monday 13 March 2023

Feathers under the microscope

The unexpected finding for me personally, on identifying feathers under the microscope, was that it was the downy feathers or down parts of feathers that can be key to identification. 

A fellow microscopist and I in Milton had missed being able to attend an Iceni meeting in Norfolk a couple of weekends ago on the topic of feathers. So later in the day, we got together to have a go ourselves. In addition to some feathers we had, we were able to borrow some from my neighbours here in Hall End.

Selection of feathers

That doesn't mean that the flight feathers are uninteresting. A closer look at the rigid part of the pheasant feather reveals the hooking mechanism on the barbules. These are the fine filaments that create the interlocking between the regular rows of  barbs radiating from the main feather stem.

Pheasant feather at 40x, 100x and 400x magnification, showing hooks and notches on barbules

Downy barbs can not only be found on (surprise surprise) down, but also on the bases of other feathers on a bird. Looked at closely, the barbs have fine filamentous barbules with distinctive nodes that can be seen at higher magnification. Below are some of the examples that we discovered.

Pheasant down at 40x, 100x and 400x magnification

Macaw down at 40x, 100x and 400x magnification

Goldfinch down at 40x, 100x and 400x magnification

Possible swan down at 40x, 100x and 400x magnification

Unknown down, possily pigeon at 40x, 100x and 400x magnification

Just to add a bit of colour, I had a go at making a stitched image of a peacock's feather, using the software Image View (which is very like Toupe View). Normally I would take separate pictures and use Hugin to stitch them together. Image View allows you to do the stitching automatically by moving the sample in rows or columns. The second attampt sort of worked, as shown below.

Eye of a peacock feather scanned with Imave View at about 40 magnification, equivalent to about 8 images stitched together.

All in all, it was a very enjoyable exercise and occupied a Sunday afternoon plus a bit extra for picture editing.

Useful identification guides for feathers under the microscope:

Microscopy of Feathers: Carla J. Dove & Sandra L. Koch, 2011. A Practical Guide for Forensic Feather Identification.  THE MICROSCOPE • Vol 59:2, pp 51-71.

Tim G. Brom, 1986. Microscopic identification of feathers and feather fragments of Palearctic birds. Bijdragen tot de Dierkunde, 56 (2): 181-204

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