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Anchorage Daily News Featured Article 11/23/00
Anchorage Daily News Featured Article 11/7/00
UPDATED REPORT!! NUMBER OF REPORTS INCREASING!!
As
of early November 1999, we had received 247 reports of Black-capped Chickadees
with grossly deformed bills within Alaska; we estimate that these represent a
minimum of 194 individuals. Many new deformed birds are continuing to be
reported this winter (1999-2000), and this report will be periodically updated
with new totals. We have also received reports of 35 individuals of 11 other
species of passerines with bill deformities, including Downy Woodpecker, Hairy
Woodpecker, Black-billed Magpie, Steller’s Jay, Northwestern Crow,
Red-breasted Nuthatch, Ruby-crowned Kinglet, Yellow-rumped Warbler, American
Robin, Pine Grosbeak, and Savannah Sparrow.
The chickadees and most of these other species are permanent residents and do not migrate. This means that whatever is causing these deformities is doing so locally, in Alaska.
WHAT DO THE DEFORMITIES LOOK LIKE?
In most cases the upper mandible is greatly elongated and curved down. The lower mandible often appears normal, but is sometimes elongated and curved up. The mandibles are often crossed. In rare cases, the upper mandible is curved in a hook shape sideways. The deformities are quite variable among individuals. Click here for more photos of Black-capped Chickadees.
WHERE ARE DEFORMED CHICKADEES BEING FOUND?
Most (60%) of the reports of deformed chickadees have come from the Matanuska-Susitna Valley, and many (35%) have been from Anchorage, where they have been clustered in the Hillside area. The rest have been reported primarily from south-central Alaska, regularly occurring as far north as Talkeetna, as far south as Homer, and as far east as Valdez and the Matanuska Glacier. There is a small cluster from the King Salmon/Dillingham area in Bristol Bay and a single report from Fairbanks. Most of the reports have been from the past two winters, but the earliest record we have is from 1991.
By comparison, we have found records of only 8 Black-capped Chickadees with bill deformities from the rest of North America. These are all of single birds from different locations and different years, dating back to 1986. These include three from Ontario, Canada, and single birds from Wisconsin, Connecticut, Washington, Minnesota, and Vermont.
Deformed birds of other species in Alaska have been found mostly in the same general areas as the chickadees--in the south-central part of the state. This past summer, however, researchers working in other parts of Alaska captured a Yellow-rumped Warbler with a crossed bill in Denali National Park and Preserve, a deformed Ruby-crowned Kinglet in Tok, and a deformed Savannah Sparrow in Yakutat.
HOW ARE THE DEFORMED BIRDS COPING WITH THEIR ABNORMAL BILLS?
Many of the chickadees whose bill deformity is not severe appear otherwise healthy. Many are quite aggressive and chase other birds away from the feeders. Chickadees with severe bill deformities have trouble manipulating and cracking open seeds. They appear to rely on suet and peanut butter to survive. Some are only able to feed by turning their heads sideways to pick up pieces of suet that have been dropped to the ground by other birds. To read about the behavior of "Cyrano," a deformed chickadee from the Wasilla area, check out Bob and Anne Winckler's observations on Cornell's Project FeederWatch web site.
Chickadees with bill deformities observed late last winter had quite dirty, ragged plumage, probably because they had difficulty preening their feathers with such deformed bills. Many birds were reported to have disappeared during a period of cold weather last January and February. Survival of these birds is probably much lower than that of normal birds because of their difficulty feeding, their increased susceptibility to predators when feeding on the ground, and their impaired ability to maintain their plumage for warmth.
WHAT IS CAUSING THESE BILL DEFORMITIES?
We
don’t know yet but are trying to determine the cause. Bill deformities are
known to be caused by many different factors, including blunt trauma to the
bill, disease, parasites, nutritional deficiencies, genetic defects, exposure to
extreme heat, and exposure to various contaminants.
In March of 1999 we examined several chickadees with bill deformities to look for evidence of what was causing the problem. We found no evidence of disease, parasites, or fractures of the bone underlying the sheath of the bill. We did find evidence of higher levels of genetic damage in the abnormal birds compared with normal birds, which can be caused by exposure to contaminants. When we tested tissues of the chickadees directly for some common contaminants, we found very low concentrations of polychlorinated biphenyls (PCBs) and DDE. These are both organochlorine compounds, which are known to cause deformities in other species, but the concentrations were too low in the chickadees to suggest that they were the cause.
We are currently examining the DNA of different deformed chickadees to see if there are any genetic links. Many people have observed several different deformed birds at their feeders, and we want to know if these birds might be siblings or parents and offspring. Because of the geographic distribution of the sightings and the rapid increase in reports over the past two years, it is unlikely that the deformities are the result of an inherited defect. It is possible, however, that parents and offspring could be exposed to whatever is causing the problem at the same time.
WHY IS IT SO DIFFICULT TO DISCOVER THE CAUSE OF THE DEFORMITIES?
There are several difficulties. First of all, bill deformities can be caused by many different factors, and it is possible that different individuals are being affected by different things. This might be true especially for the species other than chickadees. It is likely, however, that with so many records of deformed chickadees, most, if not all, of them are being affected by the same factor.
Secondly, not finding evidence of a factor does not rule it out as a cause. Many of the factors mentioned above (other than bone fracture), could cause the deformity and then have all evidence of the factor itself disappear. For example, a bird could have a bacterial infection that causes the bone to become malformed; the bird could fight off the infection and the only thing left for us to see is the deformed bill that still remains. The same thing could happen with a nutritional deficiency or contaminant. If the bird was affected much earlier than when we captured it, then it might be very difficult to find evidence of what caused the deformity.
Thirdly, we are not sure of how many birds are being affected or where they all are. What is being reported is what people see--and that means primarily birds that come to feeders during winter, where they can be seen closely enough to detect a bill deformity. When we don’t get reports from other areas or other seasons or other species, it might not be because they aren’t there. It could easily be that they are there but are just not being seen. Until we know what the true incidence and geographic distribution of deformities are, it will be difficult to pinpoint the source of the problem.
WHAT WILL BE DONE NEXT?
We will continue to study this problem to determine the cause of the deformities. There are two questions that we will try to look at first. We need to determine the true incidence of the problem--what proportion of birds are being affected and where they are. To do this, we will be asking many people across the state to watch their feeders and to report back to us the number of normal birds as well as abnormal birds that they see of each species. We are doing this in conjunction with the National Audubon Society’s annual Christmas Bird Count and with Cornell’s Project FeederWatch. This should help tell us if the geographic clusters that we have recorded so far are real or not.
We will also be working with some students from Romig Middle School in Anchorage to set up feeders in areas where there are none, such as in some parks or remote areas. They will watch the feeders to see if deformed birds also occur in areas where people do not live.
In the spring we will also be looking at nesting chickadees to see if we can detect any problems with the adults, their eggs, or nestlings. If birds are being exposed to some agent during the spring or summer, then we should have a better chance of detecting the problem by looking at birds and their offspring then. We will be setting up nest boxes in some areas so that we can easily check the eggs and nestlings of these cavity-nesting birds.
HOW CAN YOU HELP?
We are interested in knowing about any deformed birds that anyone sees. We are also interested in knowing where there are NO deformed birds being seen. Please let us know:
Please send your reports to:
Updated 29 December 1999.
Black Swifts in Alaska
In North America, the Black Swift (Cypseloides niger) breeds
along the Pacific coast and in mountainous regions of the western United States
north to British Columbia and southwestern Alberta. There are no confirmed
breeding accounts of Black Swifts from Alaska, yet they are probable rare local
breeders in the state. Observations of Black Swifts in Alaska are
rare; most come from southern Southeast Alaska, especially the Boca de Quadra
area south and east of Revillagigedo Island in Misty Fjords National
Monument. Other sightings have been reported regularly from the Stikine
Delta and the Chickamin, Unuk, Marten, and Walker Rivers. Most records are
of flocks of less than 100 individuals.
The U.S. Fish and Wildlife Service is interested in receiving information on all observations of Black Swift in Alaska. If you have information on this species in Alaska we would love to hear from you. All observations are welcome. Please include as much information as possible (e.g. location, flock size, behavior, etc.). Also include your name and a way to contact you.
Alaska Science Center - Biological Science Office