The Long-billed Hawk Syndrome...




drawing by John Schmitt

 We have recently discovered serious beak abnormalities in 60 raptors (55 Red-tailed Hawks, 2 Rough-legged Hawks, 2 Peregrine Falcons and a Ferruginous Hawk). Most of these records are from the Pacific Coast, ranging from Richmond, British Columbia to San Jose, CA. The peregrines were fall migrants caught at South Padre Island, TX. and Duluth, MN. in 2004.

The long-billed syndrome is characterized by abnormal growth of the maxilla and mandible. It was first noted in an adult Red-tailed Hawk in WA in 1997. X-rays indicate that it is caused by accelerated growth of the keratin sheath and not the underlying bone.

Adult birds of both sexes are involved as are both residents and migrants. The majority of records are adults; we have only a single example of an affected juvenile (RTHA).

As the condition develops, the maxilla extends (often grotesquely) and the overgrown beak becomes unmistakably prominent. The tip may break off and form a square or blunt end ("broken-bill" form) which apparently impedes feeding and leads to starvation. In other cases maxillae may continue to grow and eventually misalign producing the "cross-bill" form or they may curve around to enclose the mandible tip and prevent the bird from opening its beak fully ("hook-bill" form). In another example, the keratin from the mandible is forced to grow parallel inside the curve of the maxilla creating a "double sickle" form. Photo examples show details of these four types.

In most cases the keratin has a white, flaky appearance. Affected birds often carry high densities of feather lice, probably as a combined result of impeded preening and low condition. Under most circumstances affected birds are easily identified and should be reported. The cause of this syndrome is currently unknown.