A Black-capped Chickadee with a beak that has grown long and crossed
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.
Return to Ecosystems >> Terrestrial Ecosystems or Wildlife Disease and Environmental Health
Sources/Usage: Some content may have restrictions. View Media Details
We began research in 1999, and have since identified more than 3,000 affected Black-capped Chickadees in Alaska—the highest concentration of gross deformities ever recorded in a wild bird population! Increasing numbers of other species, including Northwestern Crows, Downy Woodpeckers, Steller’s Jays, and Black-billed Magpies have also been observed with beak deformities throughout the state. Growing numbers of reports from North America and Europe suggest that AKD may be spreading to a larger geographic area.
In 2016, we identified a novel picornavirus (Poecivirus) in Alaskan Black-capped Chickadees with AKD. We’ve subsequently confirmed a strong association between Poecivirus and beak deformities in chickadees and detected a closely related virus in other species with similar beak deformities. Together, this evidence suggests that Poecivirus is a likely candidate cause of AKD. Our current investigations are focusing on understanding more about this virus, including how it may be contributing to beak deformities, whether it occurs in multiple species, and how it is transmitted. Previously, we examined potential factors, such as environmental contaminants, nutritional deficiencies, and parasites, found no clear evidence linking these to AKD in Alaskan birds.
Reports from the public help us to determine where and how many birds are affected. If you see a bird with a beak deformity, please contact us.
- Beak Deformity and Banded Bird Observation Report
- 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
- Literature Cited
- Landbirds
Below are other science projects associated with this project.
Landbird Research in Alaska
On this page, learn about USGS work on Beak Deformities and Boreal Partners in Flight.
Background of Beak Deformity Research
Large numbers of Black-capped Chickadees with abnormal beaks were reported in south-central Alaska in the late 1990s. More recently, similar beak deformities have appeared in other species throughout the state. At least 30 Alaskan bird species are affected and the geographic extent of the problem appears to be growing. In addition to Alaskan observations, we have received increasing numbers of...
Species Affected by Beak Deformities
At least 30 Alaskan bird species are affected and the geographic extent of the problem appears to be growing. In addition to Alaskan observations, we have received increasing numbers of reports from other parts of North America and Europe.
Physical Description of Beak Deformities
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.
Prevalence, Distribution and Timing of Beak Deformities in Birds
The rates of beak deformities documented in Black-capped Chickadees and Northwestern Crows in Alaska are the highest ever recorded within a wild bird population anywhere.
Beak Deformity's Effects on Birds
Birds with beak deformities often have difficulty foraging and preening, and may not be able to keep themselves warm and well-fed during cold winter months. Although some birds with beak deformities breed successfully, they typically encounter more challenges than normal birds.
Possible Causes for Beak Deformities
Beak deformities can be caused by a variety of factors, including contaminants, nutritional deficiencies, disease, parasites, blunt trauma, or genetic abnormalities. We recently identified a novel picornavirus (Poecivirus) in Black-capped Chickadees with avian keratin disorder (AKD). Our results suggest that Poecivirus is the most likely factor responsible for beak deformities in Alaskan birds...
Literature Cited for Beak Deformities
Literature Cited in the Beak Deformity web pages
Links Related to Beak Deformity Research
Links, videos and news articles related to beak deformity research
Below are multimedia items associated with this project.
Black-capped Chickadee with a deformed crossed beak
A Black-capped Chickadee with a beak that has grown long and crossed
Boreal Chickadee with a mildly deformed beak
A Boreal Chickadee with a mildly deformed beak.
A Boreal Chickadee with a mildly deformed beak.
A Red-breasted Nuthatch captured at an Anchorage banding station
A Red-breasted Nuthatch captured at an Anchorage banding station
A Red-breasted Nuthatch captured at an Anchorage banding station
Black-capped Chickadee with lower elongated and upper curved beak
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight. Avian keratin disorder (AKD) is a disease characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues.
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight. Avian keratin disorder (AKD) is a disease characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues.
Black-capped Chickadee with lower elongated and upper curved beak
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight
Black-capped Chickadee with a mildly deformed beak
A Black-capped Chickadee with an upper beak slightly longer than the lower beak. Avian keratin disorder (AKD) is a disease 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.
A Black-capped Chickadee with an upper beak slightly longer than the lower beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped chickadee captured at an Anchorage banding station
A black-capped chickadee with a normal beak captured at an Anchorage banding station.
A black-capped chickadee with a normal beak captured at an Anchorage banding station.
Slate-colored Junco
A Slate-colored Junco on Middleton Island, Alaska.
A Slate-colored Junco on Middleton Island, Alaska.
Black-capped Chickadee with a deformed beak that has grown long and curved down
A Black-capped Chickadee with a beak that has grown long and curved down. Avian keratin disorder (AKD) is a disease 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.
A Black-capped Chickadee with a beak that has grown long and curved down. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a crossed beak on a branch
Black-capped Chickadee with a crossed beak on a branch.
Black-capped Chickadee with a crossed beak on a branch.
Normal Black-capped Chickadee
Normal Black-capped Chickadee
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska. Avian keratin disorder (AKD) is a disease 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.
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long down-curved elongated top beak
Black-capped Chickadee with a long down-curved elongated top beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long down-curved elongated top beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with an elongated and decurved maxilla
Black-capped Chickadee with an elongated and decurved maxilla.
Black-capped Chickadee with an elongated and decurved maxilla.
Northwestern Crow with an elongated lower beak
Northwestern Crow with an elongated lower beak. It was captured as part of the beak deformity research project. Avian keratin disorder (AKD) is a disease 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.
Northwestern Crow with an elongated lower beak. It was captured as part of the beak deformity research project. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long upper beak in the brush
Black-capped Chickadee with a long upper beak in the brush. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long upper beak in the brush. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with elongated upper beak
Black-capped Chickadee with elongated upper beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with elongated upper beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with upper long, curved down beak and crossed
Black-capped Chickadee with upper long, curved down beak and crossed. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with upper long, curved down beak and crossed. Avian keratin disorder (AKD) is a disease 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.
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.
Return to Ecosystems >> Terrestrial Ecosystems or Wildlife Disease and Environmental Health
Sources/Usage: Some content may have restrictions. View Media Details
We began research in 1999, and have since identified more than 3,000 affected Black-capped Chickadees in Alaska—the highest concentration of gross deformities ever recorded in a wild bird population! Increasing numbers of other species, including Northwestern Crows, Downy Woodpeckers, Steller’s Jays, and Black-billed Magpies have also been observed with beak deformities throughout the state. Growing numbers of reports from North America and Europe suggest that AKD may be spreading to a larger geographic area.
In 2016, we identified a novel picornavirus (Poecivirus) in Alaskan Black-capped Chickadees with AKD. We’ve subsequently confirmed a strong association between Poecivirus and beak deformities in chickadees and detected a closely related virus in other species with similar beak deformities. Together, this evidence suggests that Poecivirus is a likely candidate cause of AKD. Our current investigations are focusing on understanding more about this virus, including how it may be contributing to beak deformities, whether it occurs in multiple species, and how it is transmitted. Previously, we examined potential factors, such as environmental contaminants, nutritional deficiencies, and parasites, found no clear evidence linking these to AKD in Alaskan birds.
Reports from the public help us to determine where and how many birds are affected. If you see a bird with a beak deformity, please contact us.
- Beak Deformity and Banded Bird Observation Report
- 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
- Literature Cited
- Landbirds
Below are other science projects associated with this project.
Landbird Research in Alaska
On this page, learn about USGS work on Beak Deformities and Boreal Partners in Flight.
Background of Beak Deformity Research
Large numbers of Black-capped Chickadees with abnormal beaks were reported in south-central Alaska in the late 1990s. More recently, similar beak deformities have appeared in other species throughout the state. At least 30 Alaskan bird species are affected and the geographic extent of the problem appears to be growing. In addition to Alaskan observations, we have received increasing numbers of...
Species Affected by Beak Deformities
At least 30 Alaskan bird species are affected and the geographic extent of the problem appears to be growing. In addition to Alaskan observations, we have received increasing numbers of reports from other parts of North America and Europe.
Physical Description of Beak Deformities
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.
Prevalence, Distribution and Timing of Beak Deformities in Birds
The rates of beak deformities documented in Black-capped Chickadees and Northwestern Crows in Alaska are the highest ever recorded within a wild bird population anywhere.
Beak Deformity's Effects on Birds
Birds with beak deformities often have difficulty foraging and preening, and may not be able to keep themselves warm and well-fed during cold winter months. Although some birds with beak deformities breed successfully, they typically encounter more challenges than normal birds.
Possible Causes for Beak Deformities
Beak deformities can be caused by a variety of factors, including contaminants, nutritional deficiencies, disease, parasites, blunt trauma, or genetic abnormalities. We recently identified a novel picornavirus (Poecivirus) in Black-capped Chickadees with avian keratin disorder (AKD). Our results suggest that Poecivirus is the most likely factor responsible for beak deformities in Alaskan birds...
Literature Cited for Beak Deformities
Literature Cited in the Beak Deformity web pages
Links Related to Beak Deformity Research
Links, videos and news articles related to beak deformity research
Below are multimedia items associated with this project.
Black-capped Chickadee with a deformed crossed beak
A Black-capped Chickadee with a beak that has grown long and crossed
A Black-capped Chickadee with a beak that has grown long and crossed
Boreal Chickadee with a mildly deformed beak
A Boreal Chickadee with a mildly deformed beak.
A Boreal Chickadee with a mildly deformed beak.
A Red-breasted Nuthatch captured at an Anchorage banding station
A Red-breasted Nuthatch captured at an Anchorage banding station
A Red-breasted Nuthatch captured at an Anchorage banding station
Black-capped Chickadee with lower elongated and upper curved beak
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight. Avian keratin disorder (AKD) is a disease characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues.
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight. Avian keratin disorder (AKD) is a disease characterized by debilitating beak overgrowth and other abnormalities of keratinized tissues.
Black-capped Chickadee with lower elongated and upper curved beak
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight
A Black-capped Chickadee with a severely deformed beak where the upper beak is elongated and curved down while the lower beak is elongated and straight
Black-capped Chickadee with a mildly deformed beak
A Black-capped Chickadee with an upper beak slightly longer than the lower beak. Avian keratin disorder (AKD) is a disease 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.
A Black-capped Chickadee with an upper beak slightly longer than the lower beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped chickadee captured at an Anchorage banding station
A black-capped chickadee with a normal beak captured at an Anchorage banding station.
A black-capped chickadee with a normal beak captured at an Anchorage banding station.
Slate-colored Junco
A Slate-colored Junco on Middleton Island, Alaska.
A Slate-colored Junco on Middleton Island, Alaska.
Black-capped Chickadee with a deformed beak that has grown long and curved down
A Black-capped Chickadee with a beak that has grown long and curved down. Avian keratin disorder (AKD) is a disease 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.
A Black-capped Chickadee with a beak that has grown long and curved down. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a crossed beak on a branch
Black-capped Chickadee with a crossed beak on a branch.
Black-capped Chickadee with a crossed beak on a branch.
Normal Black-capped Chickadee
Normal Black-capped Chickadee
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska. Avian keratin disorder (AKD) is a disease 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.
Northwestern Crow with deformed top beak in Auke Bay, Juneau, Alaska. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long down-curved elongated top beak
Black-capped Chickadee with a long down-curved elongated top beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long down-curved elongated top beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with an elongated and decurved maxilla
Black-capped Chickadee with an elongated and decurved maxilla.
Black-capped Chickadee with an elongated and decurved maxilla.
Northwestern Crow with an elongated lower beak
Northwestern Crow with an elongated lower beak. It was captured as part of the beak deformity research project. Avian keratin disorder (AKD) is a disease 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.
Northwestern Crow with an elongated lower beak. It was captured as part of the beak deformity research project. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long upper beak in the brush
Black-capped Chickadee with a long upper beak in the brush. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with a long upper beak in the brush. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with elongated upper beak
Black-capped Chickadee with elongated upper beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with elongated upper beak. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with upper long, curved down beak and crossed
Black-capped Chickadee with upper long, curved down beak and crossed. Avian keratin disorder (AKD) is a disease 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.
Black-capped Chickadee with upper long, curved down beak and crossed. Avian keratin disorder (AKD) is a disease 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.