Microanatomy of passerine hard-cornified tissues: beak and claw structure of the black-capped chickadee (Poecile atricapillus).
The microanatomy of healthy beaks and claws in passerine birds has not been well described in the literature, despite the importance of these structures in avian life. Histological processing of hard-cornified tissues is notoriously challenging and only a few reports on effective techniques have been published. An emerging epizootic of beak deformities among wild birds in Alaska and the Pacific Northwest region of North America recently highlighted the need for additional baseline information about avian hard-cornified structures. In this study, we examine the beak and claw of the Black-capped Chickadee (Poecile atricapillus), a common North American passerine that is affected by what has been described as "avian keratin disorder." We use light and scanning electron microscopy and high-magnification radiography to document the healthy microanatomy of these tissues and identify features of functional importance. We also describe detailed methods for histological processing of avian hard-cornified structures and discuss the utility of special stains. Results from this study will assist in future research on the functional anatomy and pathology of hard-cornified structures and will provide a necessary reference for ongoing investigations of avian keratin disorder in Black-capped Chickadees and other wild passerine species.
US Geological Survey, Alaska Science Center, Anchorage, Alaska 99508, USA. cvanhemert@usgs.gov
Caroline
C
Van Hemert
Colleen M
CM
Handel
John E
JE
Blake
Rhonda M
RM
Swor
Todd M
TM
O'Hara
D000413:Alaska; D000818:Animals; D000835:Animals, Wild; D001502:Beak / Q000002:abnormalities / Q000648:ultrastructure*; D001715:Bird Diseases; D001717:Birds; D005260:Female; D006724:Hoof and Claw / Q000648:ultrastructure*; D007633:Keratins; D008297:Male; D009656:North America; D015205:Northwestern United States; D046109:Passeriformes / Q000033:anatomy & histology*; D012016:Reference Values
D007633:Keratins