This is an plumulaceous barbule. It is pigmented internodally but the nodes themselves are
unpigmented. The nodes are strongly spined medially.
Transmitted Circular Polarized Light
Feather barbules are the most obvious feature of a feather. They are the fibrous element that if the fluff of the down and the
surface of the flight feather. Feather barbules are of two types, pennaceous (making up the flight surface of the feather) and plumulaceous (insulation barbule).
Plumulaceous barbules are the most useful for the identification of the type of bird from which the barbule came, but the pennaceous
barbules are also useful though generally not as specific as to the type of bird.
Significance in the Environment:
Feather barbules or fragments of feather barbules are common in all indoor and outdoor environmental samples. In indoor
environments the feather barbules tend to be from furniture, clothing, or pet birds. In outdoor environments they tend to be
from song birds or other wild birds. The presence of large numbers of wild bird barbules in an indoor environment may indicate
a bird infestation in the attic of a home or near the air intake of a ventilation system. These may have health consequences.
Bird feather barbules are anisotropic with a birefringence of about 0.02. Their refractive index is around 1.54 to 1.56 and they
have a diameter of about 10 micrometers. The pennaceous barbules tend to be ribbon-shaped and the plumulaceous barbules tend to
be more circular in cross-section once away from the base of the barbule.
Dove,Carla J. and Sandra L. Koch, "Microscopy of feathers: a practical guide for forensic feather identification.",THE MICROSCOPE,
VOL. 59, NO. 2, PP. 51-71, 2011.