a growing incidence of beak deformities among Alaska's birds is ruffling environmentalists' feathers. Outsized curved beaks up to three times their normal size have been spotted in some 30 bird species of usa's largest state. In many cases, the beaks are so long that the birds are unable to feed properly, which ultimately leads to their death.

The latest sightings bring the total number of cases to around 1,800 since the first deformities were spotted in black-capped chickadees near the Anchorage city during the late 1990s. Crows in southeastern Alaska are the latest to fall victim, informs Colleen Handel of the us Geological Survey's Alaska Science Centre.

Surveys undertaken by Handel and her colleagues rule out a species-specific cause for the phenomenon. Furthermore, no disease pathogen has been tracked down to date. "In all probability, the deformities are due to organochloride pollutants such as polychlorinated biphenyls (pcbs), which are found commonly in the region,' suggests Handel. She suspects that the chemicals affect beak development in growing birds rather than causing genetic defects at birth, as newborn chicks look normal.

Other experts too blame the pollutants. "Compounds such as pcbs and dioxins can affect the birds' dna during the development process,' says Kirsty Peck, a wildlife adviser with the uk's Royal Society for the Protection of Birds. "A bird's beak is like a human fingernail: there's a part at the base where it grows. If this growth is disturbed, the beak could develop very fast or be skewed sideways,' explains Peck, adding: "This effect could leave many Alaskan birds with beaks that do not wear away naturally as they feed.'