Physical Description of Beak Deformities Active
The most commonly observed physical abnormalities among Alaskan birds are overgrown or crossed beaks. The severity of the deformities varies, ranging from a nearly indiscernible “overbite” to beaks that are more than double their normal length. The upper and lower parts of the beak are also frequently crossed or gapped.
Return to Ecosystems >> Terrestrial Ecosystems or Wildlife Disease and Environmental Health >> Beak Deformities >> Background of Beak Deformity Research
- Beak Deformity and Banded Bird Observation Report
- Beak Deformity Home
- Background
- Species Affected
- Physical Description
- Prevalence, Distribution and Timing
- Effects on Birds
- Possible Causes
- Photo Gallery - see the Multimedia tab
- Publications - see the Publications tab
- Links
- Landbirds
In a normal Black-capped Chickadee, the upper (maxilla) and lower (mandible) parts of the beak are straight and meet at the tips (Figure 3). In most affected chickadees, the maxilla is overgrown and often curves downward (Figure 4). In some cases, the beak is crossed (Figure 5) or shows a gap between the maxilla and mandible (Figure 6a). The overgrown part of the beak may be thin and brittle and sometimes breaks off, leaving a blunt tip (Figure 6b). Other birds have extremely thickened (Figure 6c) or laterally curved (Figure 6d) beaks. The deformities appear to result from overgrowth of the rhamphotheca, the outer surface of the beak which is made of keratin. Like human fingernails, the rhamphotheca grows throughout a bird’s life and is constantly worn down through pecking and feeding. X-rays of affected birds indicated that neither the cranium nor the underlying bones of the beak itself were malformed.
We conducted a captive study of Black-capped Chickadee to measure rates of beak growth in birds with AKD. We found that the beaks of affected birds grew, on average, twice as fast as those of birds with apparently normal beaks. Therefore, accelerated keratin growth appears to be the primary mechanism by which deformities develop.
Beak deformities in other species often have a similar appearance, but differ slightly among groups. Deformities in woodpeckers, flickers, and nuthatches (Figure 7a-c) generally result from extreme overgrowth, without significant crossing or curvature.
Most affected crows (Figure 8), magpies, jays (also Figure 8), and ravens, have similar growth patterns as deformed chickadees. Overgrown and downward-curving maxillas, severely elongated maxillas and mandibles, and crossed beaks are the most common corvid deformities.
Other affected passerine species, including Ruby-crowned Kinglet, American Robin, Varied Thrush, Orange-crowned, Chestnut-sided (Figure 9a) and Yellow-rumped (Myrtle) warblers (Figure 9b), Savannah and Lincoln’s sparrows, Dark-eyed and Slate-colored Junco (Figure 9c), Pine Grosbeak, Common Redpoll, Boreal Chickadee (Figure 9d), and Pine Siskin, typically exhibit beaks with crossed tips and/or varying amounts of overgrowth.
Some deformed birds also have feather or skin abnormalities (Figure 10).
See the Multimedia tab for more examples and full size versions of all of the images in the collages above.
Below are other science projects associated with this project.
Beak Deformities in Landbirds
Below are multimedia items associated with this project.
Below are publications associated with this project.
Handel, C. M., L. M. Pajot, S. M. Matsuoka, K. A. Trust, J. M. Stotts, J. Terenzi, and S. L. Talbot. 2006. Potential Role of Environmental Contaminants in the Pathology of Beak Deformities among Black-capped Chickadees in South-central Alaska. Unpb. final rpt. Project ID: 1130-7F22. U. S. Geological Survey, Alaska Science Center, Anchorage, AK.
Beak deformities in Northwestern Crows: Evidence of a multispecies epizootic
Epizootic of beak deformities among wild birds in Alaska: An emerging disease in North America?
Alaskan birds at risk: Widespread beak deformities in resident species
Use of buccal swabs for sampling DNA from nestling and adult birds
- Overview
The most commonly observed physical abnormalities among Alaskan birds are overgrown or crossed beaks. The severity of the deformities varies, ranging from a nearly indiscernible “overbite” to beaks that are more than double their normal length. The upper and lower parts of the beak are also frequently crossed or gapped.
Return to Ecosystems >> Terrestrial Ecosystems or Wildlife Disease and Environmental Health >> Beak Deformities >> Background of Beak Deformity Research
- Beak Deformity and Banded Bird Observation Report
- Beak Deformity Home
- Background
- Species Affected
- Physical Description
- Prevalence, Distribution and Timing
- Effects on Birds
- Possible Causes
- Photo Gallery - see the Multimedia tab
- Publications - see the Publications tab
- Links
- Landbirds
In a normal Black-capped Chickadee, the upper (maxilla) and lower (mandible) parts of the beak are straight and meet at the tips (Figure 3). In most affected chickadees, the maxilla is overgrown and often curves downward (Figure 4). In some cases, the beak is crossed (Figure 5) or shows a gap between the maxilla and mandible (Figure 6a). The overgrown part of the beak may be thin and brittle and sometimes breaks off, leaving a blunt tip (Figure 6b). Other birds have extremely thickened (Figure 6c) or laterally curved (Figure 6d) beaks. The deformities appear to result from overgrowth of the rhamphotheca, the outer surface of the beak which is made of keratin. Like human fingernails, the rhamphotheca grows throughout a bird’s life and is constantly worn down through pecking and feeding. X-rays of affected birds indicated that neither the cranium nor the underlying bones of the beak itself were malformed.
We conducted a captive study of Black-capped Chickadee to measure rates of beak growth in birds with AKD. We found that the beaks of affected birds grew, on average, twice as fast as those of birds with apparently normal beaks. Therefore, accelerated keratin growth appears to be the primary mechanism by which deformities develop.
Beak deformities in other species often have a similar appearance, but differ slightly among groups. Deformities in woodpeckers, flickers, and nuthatches (Figure 7a-c) generally result from extreme overgrowth, without significant crossing or curvature.
Most affected crows (Figure 8), magpies, jays (also Figure 8), and ravens, have similar growth patterns as deformed chickadees. Overgrown and downward-curving maxillas, severely elongated maxillas and mandibles, and crossed beaks are the most common corvid deformities.
Other affected passerine species, including Ruby-crowned Kinglet, American Robin, Varied Thrush, Orange-crowned, Chestnut-sided (Figure 9a) and Yellow-rumped (Myrtle) warblers (Figure 9b), Savannah and Lincoln’s sparrows, Dark-eyed and Slate-colored Junco (Figure 9c), Pine Grosbeak, Common Redpoll, Boreal Chickadee (Figure 9d), and Pine Siskin, typically exhibit beaks with crossed tips and/or varying amounts of overgrowth.
Some deformed birds also have feather or skin abnormalities (Figure 10).
See the Multimedia tab for more examples and full size versions of all of the images in the collages above.
- Science
Below are other science projects associated with this project.
Beak Deformities in Landbirds
Over the past 20 years, Alaskans have witnessed a startling increase of beak deformities among Black-capped Chickadees and other species of resident birds. This disease, called avian keratin disorder (AKD), is characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues. Affected birds have difficulty feeding and preening, and may suffer high rates of mortality. - Multimedia
Below are multimedia items associated with this project.
- Publications
Below are publications associated with this project.
Handel, C. M., L. M. Pajot, S. M. Matsuoka, K. A. Trust, J. M. Stotts, J. Terenzi, and S. L. Talbot. 2006. Potential Role of Environmental Contaminants in the Pathology of Beak Deformities among Black-capped Chickadees in South-central Alaska. Unpb. final rpt. Project ID: 1130-7F22. U. S. Geological Survey, Alaska Science Center, Anchorage, AK.
Filter Total Items: 16Beak deformities in Northwestern Crows: Evidence of a multispecies epizootic
Beak abnormalities are rare among adult birds and, typically, are not widespread in a given population, within a region, or across multiple species. A high concentration of beak deformities was recently documented in Black-capped Chickadees (Poecile atricapillus) and other resident avian species in Alaska. We describe a parallel condition in Northwestern Crows (Corvus caurinus) that signals the emAuthorsCaroline R. Van Hemert, Colleen M. HandelEpizootic of beak deformities among wild birds in Alaska: An emerging disease in North America?
The sudden appearance of a large cluster of animals with gross abnormalities may signal a significant change in an ecosystem. We describe an unusual concentration of beak deformities that appear to have arisen rapidly within Alaska and now extend southward along the Pacific Coast. In Alaska we have documented 2,160 Black-capped Chickadees (Poecile atricapillus) and 435 individuals of 29 other specAuthorsColleen M. Handel, Lisa M. Pajot, Steven M. Matsuoka, Caroline R. Van Hemert, John Terenzi, Sandra L. Talbot, Daniel M. Mulcahy, Carol U. Meteyer, Kimberly A. TrustAlaskan birds at risk: Widespread beak deformities in resident species
The team creeps silently across a well-tended lawn, eyes drawn to a small wooden box perched several meters up a lone birch tree. The first biologist is armed with a broom in one hand and a bug net in the other. Her partner wields a lunchbox-sized plastic case and a tree-climbing ladder that looks like an oversized radio antenna. A neighbor peers out her window from across the street to watch theAuthorsCaroline R. Van HemertUse of buccal swabs for sampling DNA from nestling and adult birds
We evaluated the feasibility and efficiency of using swabs to collect buccal epithelial cells fromsmall (2‐ to 13‐g) birds as a source of DNA for genetic studies. We used commercially available buccal swab kits to collect samples from 42 adult and 39 nestling (4‐ to 8‐day‐old) black‐capped chickadees (Poecile atricapillus) and from6 4‐day‐old nestling boreal chickadees (P. hudsonica). We comparedAuthorsColleen M. Handel, Lisa M. Pajot, Sandra L. Talbot, George K. Sage