©Lin Yangchen


Bird feathers are a popular subject for photomicrography, and there are already many great images that showcase the colour and beauty of their interlocking barbs. However, the substructures of individual barbules are rarely examined by microscopists outside the realm of forensic science. The nodes, pigment deposits and other morphological characteristics of barbules are not only highly fascinating but also, by virtue of their geometry and spatial distribution, enable species determination.

Forensic investigators use feather microscopy to identify species involved in cases like aircraft bird collisions and endangered species trafficking where not enough of the bird is left to identify the bird from itself. Archaeologists have even used it to identify birds used by ancient peoples (see Hargrave 1965). Wildlife conservationists could also use it to detect species that were neither seen nor heard. Feathers are easy to identify as feathers in the field and can’t be mistaken for other kinds of animals.

To the author’s knowledge, as of 2021, the microscopic feather structures of Southeast Asian birds have never been surveyed. The specimens shown here illustrate the potential for more research in this area. No birds were harmed; all feathers were already separated naturally when picked up. For serious work a reference collection is needed, such as the 2,400 feather microslides in the National Museum of Natural History in Washington, D.C.

Barbules are relatively easy to prepare for microscopical examination. A downy barb at the base of the feather is pulled off with a pair of fine forceps and floated on a drop of water on a microscope slide to spread the barbules, and a coverslip is added. If available, Histosolve or xylene should be used in place of water to avoid air pockets caused by the surface tension of water. For a permanent mount, just let the slide dry and add Flo-texx (or other mountant of similar refractive index to water) before adding the coverslip (Dove & Koch 2011). Micrographs were taken with the author’s ‘Special Forces’ Olympus BHSP polarizing microscope.


Click individual specimens:


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Accession no. F001


unknown species



Internodal pigment distribution.




Accession no. F002


unknown species



Triangular nodes and uniform nodal pigment.


Length-slow keratin with 530 nm retardation plate.

Measurement of retardation with de Sénarmont compensation. This, along with the diameter of the barbule, can be used to determine birefringence and check whether a fragment too small to be visually identified as a feather is made of keratin.




Accession no. F003


Chalcophaps indica
emerald dove



Spine nodes.




Accession no. F004


Halcyon pileata
black-capped kingfisher



Unpigmented spine nodes.




Accession no. F005


Gallus gallus
red junglefowl



Closely spaced nodes with internodal pigment.




Accession no. 006


Amaurornis phoenicurus
white-breasted water hen



Pronounced spines with dense internodal pigment.




Accession no. F007


Pycnonotus goiavier
yellow-vented bulbul



Unpigmented spine nodes with background yellow pigment.




References


Global feather atlas
North American feather atlas


Dove, C. J. 1997. Quantification of microscopic feather characters used in the identification of North American plovers. The Condor 99:47–57.

Dove, C. J. & Koch, S. L. 2011. Microscopy of feathers: a practical guide for forensic feather identification. The Microscope 59(2):51—71.

Hargrave, L. L. 1965. Identification of feather fragments by microstudies. Memoirs of the Society for American Archaeology 19:202–205.

Wheeler, B. P. 2021. Practical Forensic Microscopy: a Laboratory Manual. John Wiley & Sons, United Kingdom.

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