Oiled Common Murre being washed
Impacts of Oil on Seabirds
Feathers & Skin
The primary problem caused when a bird comes into contact with oil is a physical alteration of the feather structure. Feathers are made up of an interlocking structure of barbs and barbules - similar to Velcro(r) - that keeps cold water out and warm air next to the skin. Natural oils produced by the bird help to condition the feathers so they do not break as readily, but they do not directly aid in waterproofing. When oiled, feathers lose this ability to trap air and repel water. As a result, birds no longer maintain body heat and become hypothermic. To combat this decrease in body temperature, their metabolism increases, causing a greater need for food. At the same time, these birds do not float well; their swimming and foraging ability decreases; and they often cannot fly and will haul out of the water. Lighter, more volatile petroleum products (such as kerosene and jet fuel) can also cause significant skin burns and eye irritation.
Because birds preen themselves meticulously to maintain their insulating air layer, external oiling almost always leads to some oil ingestion. Once oil is ingested, it can cause direct damage to the gastrointestinal tract, evidenced by ulcers, diarrhea, and a decreased ability to absorb nutrients. If the volatile components of the oil are inhaled, it can lead to pneumonia, neurological damage, or absorption of chemicals that can lead to cancer. Metabolism of the oil components by the kidney and liver can lead to extensive damage to those organs as well. Last, oil (and the stress of being oiled) can cause birds to have significant anemia and the lack of blood cells that combat infection.
Oil can have drastic effects on each stage of bird reproduction. Studies on the effects of a single drop of oil on eggs from different species of birds have shown significant mortality and developmental defects in affected embryos. Other research has shown increased abandonment of hatchlings as well as alterations in breeding activities by adult birds.
Long-term effects of oiling on bird populations are difficult to assess because of the challenges with following animals after release. Early post-release studies showed that birds did not survive well after oiling, and therefore may not have significantly contributed to the population as a whole. These studies, however, used few data upon which to base their conclusions. This lack of information is actively being addressed by the OWCN through the funding of selected post-release research projects. These studies suggest that birds survive for longer periods of time following oil exposure and rehabilitation than previously reported. Other studies conducted following rehabilitation (using non-OWCN protocols) have found variable survival rates and behavioral effects of oiling and rehabilitation in pelicans, coots, murres, and penguins.