A Black-capped Chickadee with a beak that has grown long and crossed
Beak Deformities in Landbirds Active
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
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
Background of Beak Deformity Research
Species Affected by Beak Deformities
Physical Description of Beak Deformities
Prevalence, Distribution and Timing of Beak Deformities in Birds
Beak Deformity's Effects on Birds
Possible Causes for Beak Deformities
Literature Cited for Beak Deformities
Links Related to Beak Deformity Research
Below are data associated with this project.
Data Associated with Poecivirus Testing of Individual Birds with Beak Deformities
Below are multimedia items associated with this project.
A Black-capped Chickadee with a beak that has grown long and crossed
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 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.
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
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.
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.
A Slate-colored Junco on Middleton Island, Alaska.
A Slate-colored Junco on Middleton Island, Alaska.
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.
Normal Black-capped Chickadee
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. 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.
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. 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. 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. 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.
Below are publications associated with this project.
Poecivirus is present in individuals with beak deformities in seven species of North American birds
Avian keratin disorder of Alaska black-capped chickadees is associated with Poecivirus infection
Blood serum chemistry of wild Alaskan Black-capped Chickadees (Poecile atricapillus) with avian keratin disorder
Elements in whole blood of Northwestern Crows (Corvus caurinus) in Alaska: No evidence for an association with beak deformities
Avian malaria in a boreal resident species: long-term temporal variability, and increased prevalence in birds with avian keratin disorder
Novel picornavirus associated with avian keratin disorder in Alaskan birds
Isolation of a complete circular virus genome sequence from an Alaskan black-capped chickadee (Poecile atricapillus) gastrointestinal tract sample.
Environmental contaminants and chromosomal damage associated with beak deformities in a resident North American passerine
Macroscopic, histologic, and ultrastructural lesions associated with avian keratin disorder in Black-capped Chickadees (Poecile atricapillus)
Evidence of accelerated beak growth associated with avian keratin disorder in black-capped chickadees (Poecile atricapillus)
Microanatomy of passerine hard-cornified tissues: Beak and claw structure of the black-capped chickadee (Poecile atricapillus)
Stable isotopes identify dietary changes associated with beak deformities in Black-Capped Chickadees (Poecile atricapillus)
- Overview
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
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
- Science
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 pagesLinks Related to Beak Deformity Research
Links, videos and news articles related to beak deformity research - Data
Below are data associated with this project.
Data Associated with Poecivirus Testing of Individual Birds with Beak Deformities
This data set is comprised of two tables, one with results of poecivirus screening of tissues from six North American avian species using PCR followed by Sanger sequencing in addition to unbiased metagenomic sequencing, the second lists the names and sequences of primers used. - Multimedia
Below are multimedia items associated with this project.
Black-capped Chickadee with a deformed crossed beakBlack-capped Chickadee with a deformed crossed beakA 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 beakA Boreal Chickadee with a mildly deformed beak.
A Boreal Chickadee with a mildly deformed beak.
A Red-breasted Nuthatch captured at an Anchorage banding stationA Red-breasted Nuthatch captured at an Anchorage banding stationA 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 beakBlack-capped Chickadee with lower elongated and upper curved beakA 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 beakBlack-capped Chickadee with lower elongated and upper curved beakA 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 beakBlack-capped Chickadee with a mildly deformed beakA 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 stationBlack-capped chickadee captured at an Anchorage banding stationA 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 JuncoA 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 downBlack-capped Chickadee with a deformed beak that has grown long and curved downA 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 branchBlack-capped Chickadee with a crossed beak on a branchBlack-capped Chickadee with a crossed beak on a branch.
Black-capped Chickadee with a crossed beak on a branch.
Normal Black-capped ChickadeeNormal Black-capped Chickadee
Northwestern Crow with deformed top beak in Auke Bay, Juneau, AlaskaNorthwestern Crow with deformed top beak in Auke Bay, Juneau, AlaskaNorthwestern 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 beakBlack-capped Chickadee with a long down-curved elongated top beakBlack-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 maxillaBlack-capped Chickadee with an elongated and decurved maxillaBlack-capped Chickadee with an elongated and decurved maxilla.
Black-capped Chickadee with an elongated and decurved maxilla.
Northwestern Crow with an elongated lower beakNorthwestern 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 brushBlack-capped Chickadee with a long upper beak in the brushBlack-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 beakBlack-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 crossedBlack-capped Chickadee with upper long, curved down beak and crossedBlack-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.
- Publications
Below are publications associated with this project.
Filter Total Items: 17Poecivirus is present in individuals with beak deformities in seven species of North American birds
Avian keratin disorder (AKD), a disease of unknown etiology characterized by debilitating beak overgrowth, has increasingly affected wild bird populations since the 1990s. A novel picornavirus, poecivirus, is closely correlated with disease status in Black-capped Chickadees (Poecile atricapillus) in Alaska. However, our knowledge of the relationship between poecivirus and beak deformities in otherAuthorsMaxine Zylberberg, Caroline R. Van Hemert, Colleen M. Handel, Rachel Liu, Joseph L. DeRisiAvian keratin disorder of Alaska black-capped chickadees is associated with Poecivirus infection
BackgroundAvian keratin disorder (AKD) is an epizootic of debilitating beak deformities, first documented in black-capped chickadees (Poecile atricapillus) in Alaska during the late 1990s. Similar deformities have now been recorded in dozens of species of birds across multiple continents. Despite this, the etiology of AKD has remained elusive, making it difficult to assess the impacts of this diseAuthorsMaxine Zylberberg, Caroline R. Van Hemert, Colleen M. Handel, Joseph L. DeRisiBlood serum chemistry of wild Alaskan Black-capped Chickadees (Poecile atricapillus) with avian keratin disorder
We measured serum chemistries in wild Black-capped Chickadees (Poecile atricapillus) from Alaska to test for potential differences associated with beak deformities characteristic of avian keratin disorder. Lower uric acid in affected birds was the only difference detected between groups, although sample sizes were small. This difference could be associated with fasting or malnutrition in birds witAuthorsCaroline R. Van Hemert, Colleen M. HandelElements in whole blood of Northwestern Crows (Corvus caurinus) in Alaska: No evidence for an association with beak deformities
A recent outbreak of beak deformities among resident birds in Alaska has raised concern about environmental contamination as a possible underlying factor. We measured whole blood concentrations of 30 essential and nonessential elements to determine whether any were associated with beak deformities in Northwestern Crows (Corvus caurinus). We tested for differences between 1) adults with versus thosAuthorsCaroline R. Van Hemert, Colleen M. HandelAvian malaria in a boreal resident species: long-term temporal variability, and increased prevalence in birds with avian keratin disorder
The prevalence of vector-borne parasitic diseases is widely influenced by biological and ecological factors. Environmental conditions such as temperature and precipitation can have a marked effect on haemosporidian parasites (Plasmodium spp.) that cause malaria and those that cause other malaria-like diseases in birds. However, there have been few long-term studies monitoring haemosporidian infectAuthorsLaura C. Wilkinson, Colleen M. Handel, Caroline R. Van Hemert, Claire Loiseau, Ravinder N. M. SehgalNovel picornavirus associated with avian keratin disorder in Alaskan birds
Avian keratin disorder (AKD), characterized by debilitating overgrowth of the avian beak, was first documented in black-capped chickadees (Poecile atricapillus) in Alaska. Subsequently, similar deformities have appeared in numerous species across continents. Despite the widespread distribution of this emerging pathology, the cause of AKD remains elusive. As a result, it is unknown whether suspecteAuthorsMaxine Zylberberg, Caroline R. Van Hemert, John P. Dumbacher, Colleen M. Handel, Tarik Tihan, Joseph L. DeRisiIsolation of a complete circular virus genome sequence from an Alaskan black-capped chickadee (Poecile atricapillus) gastrointestinal tract sample.
We report here the genome sequence of a circular virus isolated from samples of an Alaskan black-capped chickadee (Poecile atricapillus) gastrointestinal tract. The genome is 2,152 bp in length and is most similar (30 to 44.5% amino acid identity) to the genome sequences of other single-stranded DNA (ssDNA) circular viruses belonging to the gemycircularvirus group.AuthorsZachary R. Hanna, Charles Runckel, Jerome Fuchs, Joseph L. DeRisi, David P. Mindell, Caroline R. Van Hemert, Colleen M. Handel, John P. DumbacherEnvironmental contaminants and chromosomal damage associated with beak deformities in a resident North American passerine
A large cluster of beak abnormalities among black-capped chickadees (Poecile atricapillus) in Alaska raised concern about underlying environmental factors in this region. Metals and trace elements, organochlorine pesticides, polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-dioxins and polychlorinated dibenzofurans (PCDD-Fs) were analyzed in adults, nestlings, and eggs of the affectedAuthorsColleen M. Handel, Caroline R. Van HemertMacroscopic, histologic, and ultrastructural lesions associated with avian keratin disorder in Black-capped Chickadees (Poecile atricapillus)
An epizootic of beak abnormalities (avian keratin disorder) was recently detected among wild birds in Alaska. Here we describe the gross, histologic, and ultrastructural features of the disease in 30 affected adult black-capped chickadees (Poecile atricapillus). Grossly, there was elongation of the rhamphotheca, with varying degrees of lateral deviation, crossing, and gapping between the upper andAuthorsCaroline R. Van Hemert, A. G. Armién, J.E. Blake, Colleen M. Handel, T. M. O'HaraEvidence of accelerated beak growth associated with avian keratin disorder in black-capped chickadees (Poecile atricapillus)
We recently documented an epizootic of beak deformities in more than 2,000 Black-capped Chickadees (Poecile atricapillus) and other wild bird species in North America. This emerging avian disease, which has been termed avian keratin disorder, results in gross overgrowth of the rhamphotheca, the outer, keratinized layer of the beak. To test the hypothesis that the beak deformities characteristic ofAuthorsCaroline R. Van Hemert, Colleen M. Handel, Todd M. O'HaraMicroanatomy 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 NoAuthorsCaroline R. Van Hemert, Colleen M. Handel, John E. Blake, Rhonda Swor, Todd M. O'HaraStable isotopes identify dietary changes associated with beak deformities in Black-Capped Chickadees (Poecile atricapillus)
A large number of beak deformities of unknown etiology have recently been reported in Black-capped Chickadees (Poecile atricapillus) and other resident avian species in Alaska. We investigated the potential association between diet and beak deformities. We analyzed carbon (δ13C) and nitrogen (δ15N) isotopes in whole blood of Black-capped Chickadees captured at three semiurban sites in south-centraAuthorsCaroline R. Van Hemert, Colleen M. Handel, Diane M. O'Brien