Image source: Bird Holidays
If the ivory gull could, it would tell that polar bear, 'I wouldn't eat that if I were you' - eating carcasses of other animals is what got the ivory gull in this predicament in the first place. The ivory gull, which lives in the Arctic, was recently found to have the highest concentrations of PCBs and DDT when its eggs were tested. The more interesting point is that both of these chemicals are banned in many countries, though DDT is still used to control disease vectors in some countries. How did this bird get top prize? Well, the prevailing winds sweep these chemicals from around the globe and concentrate them in a swirling mass in the Arctic. From here, the chemicals accumulate in the fatty tissues of birds, fish and other animals. Ivory gulls are top predators, meaning they eat fish and scavenge dead seals and polar bears. Any chemicals that are in these animals are then passed onto the gulls, so basically the gulls are eating DDT and PCBs for dinner every night.
The UN banned 12 of the most persistent organic pollutants, the "dirty dozen", and levels of these in the Arctic have been falling but they are still present. Scientists began looking at the ivory gull after there were reports of 80% population loss. PCBs can shorten the lifespan of the gulls and thin their eggs making it harder to produce offspring. The thinning sea ice also affects the lifespan of the gulls because they feed on fish and plankton around the fringes of the ice. (Is there anything the thinning ice doesn't harm?)
Scientists are still unsure why concentrations are higher in the gulls as compared to other Arctic wildlife. Levels of the chemicals in the egg shells tested at the same levels that were seen in polar bears 20 years ago.
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