Prevalence, Distribution and Timing of Beak Deformities in Birds
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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.
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Deformed beak Black-capped Chickadee next to peanut butter on a feeder
(Credit: Lee Tibbitts, USGS, Alaska Science Center. Public domain.)
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Since the 1990's, prevalence of avian keratin disorder (AKD) has clearly increased in Alaska and now affects an estimated 6.5% (±0.5%) of adult Black-capped Chickadees and 16.9% (±5.3%) of adult Northwestern Crows.
Typically, abnormal beaks are relatively rare among adult birds, and background levels are less than 0.5% in normal populations. The prevalence we measured in chickadees was four times higher than the maximum rate previously documented for any passerine (Pomerory 1962). For crows, this estimate was more than 15 times higher.
Based on reports from the late 1990s, two epicenters of AKD among Black-capped Chickadees were first identified: one in the Mat-Su Valley and one in Bristol Bay. Beak deformities initially appeared to be clustered in south-central Alaska, where most chickadees with beak deformities have been observed. However, relatively large numbers of chickadees and other species have recently been observed with deformities in the Fairbanks area of central Alaska. We have also documented chickadees with beak deformities at remote locations in south-central Alaska.
Beak deformities among other species, including crows, appear to be increasing in Alaska and throughout the Pacific Northwest. In addition, recent reports from other parts of North America and Europe, particularly the United Kingdom, suggest that this problem may affect a large geographic area.
Developmentally, birds appear to develop beak deformities as adults, rather than as embryos or nestlings, suggesting that they are not congenital in nature. Very few young birds had obvious deformities, as compared to high rates in adults. Most deformities were very subtle in onset, however, with slight overgrowth or asymmetry of the beak. Based on results from our winter banding study, there seems to be a higher probability of deformities developing during late winter than during other parts of the year.
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Date published: August 22, 2017Status: ActiveBeak 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...
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Date published: August 21, 2018Status: ActiveBackground 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...
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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.
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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.
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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...
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Date published: August 15, 2018Status: ActiveLiterature Cited for Beak Deformities
Literature Cited in the Beak Deformity web pages
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Date published: August 14, 2018Status: ActiveLinks Related to Beak Deformity Research
Links, videos and news articles related to beak deformity research
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.
Steller's Jay with deformed beak at a bird feeder
A Steller's Jay with a deformed beak at a bird feeder. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
Chestnut-sided Warbler with deformed beak
A Chestnut-sided Warbler with an unusually long beak sitting in a tree. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
Northern Flicker with a grossly crossed beak at a suet block
Northern Flicker with a grossly crossed beak hanging from a suet block. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
Northern Flicker with a grossly crossed beak in a tree
Northern Flicker with a grossly crossed beak sitting in a tree. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
Northern Flicker with a grossly crossed beak
Northern Flicker with a grossly crossed beak. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
Northern Flicker with a grossly crossed beak in the grass
Northern Flicker with a grossly crossed beak in the grass. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
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 Beak Deformity
Typical beak deformity in a (Poecile atricapillus) affected by avian keratin disorder in Anchorage, Alaska
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
Steller's Jay with lower beak longer than upper beak
A Steller's Jay with a deformed beak, the bottom being longer than the top. This photo was from an observation report of the Alaska Science Center's Beak Deformity project.
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