Microscopy of Feathers: A Practical Guide for Forensic Feather Identification1

The identification of bird species from feather fragments is useful in many disciplines, including forensic science. Feather evidence can be helpful to criminal investigations in demonstrating physical contact between clothing manufactured with down feathers, or it may provide specific links to the crime scene by identifying the species or group of birds from which the feather evidence came. This guide describes the potential importance of feather evidence to criminal investigations and introduces the basic techniques of approaching the identification of birds from feather evidence in such cases. Photomicrographs and descriptions are provided for eight (8) orders of birds that are commonly involved in criminal cases with emphasis on the diagnostic microscopic characters for each order. Characteristics of feather barbs, barbules, nodes and pigmentation patterns are described in detail with cautionary notes for similar species in each group. Also discussed are details of feather topography, microslide preparation for downy (plumulaceous) feather barbs, information on report writing and testimony, and the significance of feathers in forensic cases. INTRODUCTION Interspecific variation in the microscopic characters of plumulaceous (downy) feathers was first investigated by Chandler (1). Although his work demonstrated the importance of microscopic feather characters to avian systematics, the process of identifying birds from feather fragments has since been applied to a wide variety of studies. Some of the current applications of feather identification include identifying birds that collide with aircraft (bird strikes), ecological studies of prey remains, food contamination investigations, and law enforcement cases for agencies such as U.S. Customs, U.S. Fish and Wildlife Service, the National Park Service and the Federal Bureau of Investigation (FBI). During the course of a criminal investigation, the feather evidence may be helpful in demonstrating physical contact between clothing manufactured with down feathers or may provide specific links to the crime scene by identifying the species or group of birds from which the feather evidence came. Objectives The objectives of “Microscopy of Feathers: A Practical Guide for Forensic Feather Identification” are twofold: 1) To increase awareness of the potential importance of feather evidence to criminal investigations, and 2) to introduce the basic techniques of approaching the identification of birds from feather evidence in criminal cases. 1Originally published online in the Journal of the American Society of Trace Evidence Examiners, Vol. 1, No. 1, June 2010, www.asteetrace.org. *NHB E-600, MRC 116, PO Box 37012, Washington, D.C. **2501 Investigation Parkway, Quantico, VA 22135 52 THE MICROSCOPE 59 (2011) Cautions, Convergences and Disclaimers This guide is intended to focus on the preparation, examination and comparison of microscopic feather evidence in a forensic setting. Photomicrographs and microscopic feather characteristics for selected species, which are most likely to be involved in criminal cases, are presented and described here. They are intended to provide guidance for the identification of feather fragments but are not meant to be used as a sole source of identification. Due to the large variation in feather structures between species, within species and even sometimes within the same feathers, users of this guide should consult an ornithologist before assigning positive species identifications to feather samples. The diagnostic microscopic characteristics described in this guide are helpful to identify groups, or orders, of birds. Not all members of a particular group, nor all of the feather types or even all of the barbs, will have the diagnostic characters needed for identification. Also, when incomplete feathers or small samples are all that is available for examination, it may not be possible to determine any information about the feather sample. It is always best to have multiple barbs with many diagnostic features before confidently assigning an unknown feather sample to a group of birds. Finally, morphological convergences do occur in plumulaceous (downy) feather structures. The microscopic structures of downy feathers of birds that occupy the same environments may have “converged” to appear similar even though the birds are not closely related. An example of this occurs in grebes, loons and alcids (2). All of these birds live in aquatic environments, dive for food and have similar microscopic downy feather characteristics, even though they are not closely related to each other nor do they resemble one another in physical appearance. Convergences may also occur in other groups but are not typical of birds that are involved in criminal investigations. Laws Protecting Birds All species of birds native to North America are considered migratory and, therefore, are protected by the Migratory Bird Treaty Act (MBTA). This treaty also prohibits the possession of feathers and other bird parts (i.e. nests, talons, feathers, etc.) of native species without permission. Therefore, any feathers or bird parts found in a criminal investigation are probably illegal and should be suspect. The only exceptions involve feathers taken from introduced non-protected species or legally hunted waterfowl or other migratory game birds, which may be possessed by hunters. This prohibition extends to molted feathers and to feathers taken from roador window-killed birds. Individuals or institutions wishing to use bird feathers, bones, bird parts or whole specimens for educational or research purposes must apply for permits from the U.S. Fish and Wildlife Service and their state wildlife or natural resource agency. For more information, go online to www.fws.gov/migratorybirds/ mbpermits.html. Some species are also protected by additional statutes such as the Endangered Species Act (ESA) and the Bald and Golden Eagle Protection Act (BGEPA). The list of North American birds protected by the MBTA can be found at www.fws.gov/ m i g r a t o r y b i r d s / R e g u l a t i o n s P o l i c i e s / m b t a / mbtintro.html.