Species Affected

A total of 29 species, including 18 residents and 11 migrants, have been reported with beak deformities in Alaska (Table 1).

For more information on specific groups of birds, follow the links below:

| Black-capped Chickadees | Northwestern Crows | Other Species |

Table 1. List of species observed with beak deformities in Alaska

Black-capped Chickadees

A cluster of beak deformities among Black-capped Chickadees in Alaska has attracted significant public attention in recent years.  Approximately 10% of adult birds are affected, which is the highest concentration ever recorded within a wild bird population anywhere!

Large numbers of deformed Black-capped Chickadees were first reported in the late 1990s and biologists at the Alaska Science Center began research in 1999.  Approximately 500 nest boxes in Anchorage, Eagle River, and the Matanuska-Susitna Valley were monitored during the summers of 2000-2004.  In November of 2001 we began an ongoing winter banding study to determine the age and sex of affected birds.  In addition, this study has allowed us to identify differences in the numbers of beak deformities that have developed between seasons and years.

With help from the public, we have documented over 1,900 reports of Black-capped Chickadees with deformed beaks in Alaska (see map; Figure 1).  Deformed birds occur primarily in south-central Alaska, but have been increasingly reported from western and central parts of the state.  The first deformed Black-capped Chickadees were observed in winter 1991-1992.  That winter, single chickadees with deformed beaks were seen in King Salmon and Naknek in the Bristol Bay region and in Wasilla and near Nancy Lakes in the Mat-Su Valley. 

By comparison, few responses from outside of Alaska have been received from inquiries through Project FeederWatch, bulletin boards, and response to national media coverage.  Although they are year-round residents across forested regions of Canada and the northern two-thirds of the contiguous United States, fewer than 25 Black-capped Chickadees with deformed beaks have been documented from outside of Alaska.

Chickadees are resident throughout Alaska and other parts of their range and are generally associated with deciduous or deciduous/coniferous forests.  They are primary cavity nesters, excavating holes predominantly in rotten wood of softwood trees (Smith 1991) and have several adaptations for surviving the extreme cold and short photoperiod characteristic of winter at high latitudes.  Chickadees often enter a state of regulated hypothermia at night (Chaplin 1974, 1976; Sharbaugh 2001), store and metabolize large amounts of fat daily (Chaplin 1974), and have a well developed spatial memory to relocate cached food (Hitchcock and Sherry 1990, Pravosudov and Lucas 2000, Pravosudov and Clayton 2002).

Northwestern Crows and Other Corvids

Although we have not yet determined the prevalence of beak deformities among corvids (the family of birds that includes crows, ravens, jays, and magpies), nearly 200 individuals have been documented in Alaska.  The frequency of sightings of deformed Northwestern Crows, Common Ravens, Black-billed Magpies, and Steller’s Jays suggests that prevalence is higher than the normal background level for these species. 

Northwestern Crow, photo by Jack Whitman

In particular, we have received growing numbers of reports of Northwestern Crows with beak deformities, and the total number of documented observations for this species is second only to that of Black-capped Chickadees.  Crows with beak deformities have been reported in south-central Alaska and along the coast to south-east Alaska, British Columbia, and Puget Sound in Washington State (see map; Figure 2).  More than 130 deformed crows have been documented in Alaska alone.  At least 50 additional birds have been identified across the rest of the Pacific Northwest.  We have been soliciting reports from the public in Alaska, British Columbia, and Washington State and this information is helping us to determine the number of birds affected and the geographic extent of these deformities. In addition, ongoing capture efforts throughout coastal Alaska have documented beak deformities at rates higher than normal background levels (see Current Research)

Although corvids overlap geographically with Black-capped Chickadees within the same broad region, there are significant differences in habitats used, particularly among Northwestern Crows.  Unlike insect- and seed-eating chickadees, crows normally feed in the intertidal zone on mussels and other filter feeders.  Presence of deformities in this species indicates that factors contributing to beak abnormalities occur in both terrestrial and marine/intertidal systems.

Other Species

In addition to Black-capped Chickadees, Northwestern Crows, Black-billed Magpies, Common Ravens, and Gray and Steller’s jays, 23 other species have been documented in Alaska with beak deformities.  Black-capped Chickadees have been the most commonly reported species, followed by Northwestern Crow, Red-breasted Nuthatch, Black-billed Magpie, Steller’s Jay, and Downy Woodpecker (Table 2).

Table 2. Most frequently documented species with beak deformities in Alaska.

Resident species include Red-breasted Nuthatches and Downy and Hairy woodpeckers, which are commonly reported with unusually long beaks.  Despite their use of habitats similar to nuthatches, woodpeckers, and Black-capped Chickadees, only five Boreal Chickadees and one Chestnut-backed Chickadee have been reported with beak deformities. 

Among migratory species, 16 individuals of 10 passerine species have been documented with beak deformities in Alaska.  Among these, nearly all were juvenile birds captured or observed during autumn, meaning that they had been produced in the state.  Therefore, we assume that these individuals developed beak deformities while in Alaska and before leaving for wintering areas. 

Deformed beaks have also been recorded from waterbirds and raptors (Table 1), including at least three Pelagic Cormorants and one Pacific Loon seen near Sitka, one Black-legged Kittiwake near Cordova, two adult Bald Eagles on the Kenai Peninsula, and one nestling Peregrine Falcon on the Colville River in northern Alaska.