Beak Deformities in Landbirds
Science Center Objects
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.
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A Black-capped Chickadee with a deformed beak trying to eat at a suet ball
(Credit: Sherry Shiesl. Courtesy: Sherry Shiesl)
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
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- Literature Cited
- Landbirds
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Date published: July 13, 2017Status: ActiveLandbird Research in Alaska
Beak Deformities, Boreal Partners in Flight and USGS Changing Arctic Ecosystems Boreal-Arctic Transition Zone.
Attribution: Ecosystems, Alaska Science Center
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Date published: August 21, 2018Status: Active
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...
Attribution: Alaska Science Center -
Date published: August 20, 2018Status: ActiveSpecies 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.
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Date published: August 19, 2018Status: ActivePhysical 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.
Attribution: Alaska Science Center -
Date published: August 18, 2018Status: ActivePrevalence, 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.
Attribution: Alaska Science Center -
Date published: August 17, 2018Status: ActiveBeak 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.
Attribution: Alaska Science Center -
Date published: August 16, 2018Status: ActivePossible 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...
Attribution: Alaska Science Center -
Date published: August 15, 2018Status: ActiveLiterature Cited for Beak Deformities
Literature Cited in the Beak Deformity web pages
Attribution: Alaska Science Center -
Date published: August 14, 2018Status: ActiveLinks Related to Beak Deformity Research
Links, videos and news articles related to beak deformity research
Attribution: Alaska Science Center
Avian 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,...
Zylberberg, Maxine; Van Hemert, Caroline R.; Handel, Colleen M.; DeRisi, Joseph L. Novel 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...
Zylberberg, Maxine; Van Hemert, Caroline R.; Dumbacher, John P.; Handel, Colleen M.; Tihan, Tarik; DeRisi, Joseph L. Blood 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...
Van Hemert, Caroline R.; Handel, Colleen M. Elements 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...
Van Hemert, Caroline R.; Handel, Colleen M. Avian 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...
Wilkinson, Laura C.; Handel, Colleen M.; Van Hemert, Caroline R.; Loiseau, Claire; Sehgal, Ravinder N. M. Isolation 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...
Hanna, Zachary R.; Runckel, Charles; Fuchs, Jerome; DeRisi, Joseph L.; Mindell, David P.; Van Hemert, Caroline R.; Handel, Colleen M.; Dumbacher, John P. Environmental 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...
Handel, Colleen M.; Van Hemert, Caroline R. Macroscopic, 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...
Van Hemert, Caroline R.; Armién, A. G.; Blake, J.E.; Handel, Colleen M.; O'Hara, T. M. Stable 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...
Van Hemert, Caroline R.; Handel, Colleen M.; O'Brien, Diane M. Evidence 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...
Van Hemert, Caroline R.; Handel, Colleen M.; O'Hara, Todd M. 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...
Van Hemert, Caroline R.; Handel, Colleen M.; Blake, John E.; Swor, Rhonda; O'Hara, Todd M. A natural experiment on the condition-dependence of achromatic plumage reflectance in black-capped chickadees
Honest advertisement models posit that only individuals in good health can produce and/or maintain ornamental traits. Even though disease has profound effects on condition, few studies have experimentally tested its effects on trait expression and even fewer have identified a mechanistic basis for these effects. Recent evidence suggests that black...
D'Alba, L.; Van Hemert, Caroline R.; Handel, Colleen M.; Shawkey, M.D.-
Date published: April 1, 2018Genetic Data Associated with Avian Keratin Disorder and Poecivirus in Black-capped Chickadees, Alaska, 2001-2017
This dataset contains results of genetic screening for Poecivirus from samples of black-capped chickadees (BCCH; Poecile atricapillus) with and without clinical signs of avian keratin disorder (AKD). Data include information on detection/non-detection of the virus in tissue collected with buccal swabs, cloacal swabs, blood samples, and fecal samples from up to 124 individuals between 2015 and...
Attribution: Alaska Science Center
Black-capped chickadee with a deformed beak
Black-capped chickadee with a deformed beak
Black-capped Chickadee with a deformed crossed beak
A Black-capped Chickadee with a beak that has grown long and crossed
Black-capped Chickadee with a deformed beak
A Black-capped Chickadee with a beak that has grown long and curved down
Black-capped Chickadee with a mildly deformed beak
A Black-capped Chickadee with an upper beak slightly longer than the lower beak
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
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
Boreal Chickadee with a mildly deformed beak
A Boreal Chickadee with a mildly deformed beak.
Black-capped Chickadee with a deformed beak on a suet ball
A Black-capped Chickadee with a deformed beak trying to eat at a suet ball
Black-capped chickadee captured at an Anchorage banding station
A black-capped chickadee with a normal beak 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
Slate-colored Junco
A Slate-colored Junco on Middleton Island, Alaska.
A Yellow-rumped Warbler with a deformed beak, Cape May, New Jersey
A Yellow-rumped (Myrtle) Warbler with a crossed beak sitting in a tree in Cape May, New Jersey.