With the rise of global industrialization and a rapidly expanding consumer culture, marine plastic pollution is fast becoming an existential threat to seabirds. Birds that live and feed on the open sea, such as albatrosses and fulmars (above), often mistake floating plastic for prey.
Over time, this ingestion can kill the animal, and in many cases, adult birds will regurgitate plastic when feeding their young. The upcoming documentary Midway (see below) highlights this problem with stark and heartbreaking footage.
Researchers seeking to better understand the extent of the problem have now found that by measuring levels of certain chemical compounds in preening oil, they are able to estimate the level of ingestion in a bird. Previous methods of determining plastic volume in a live bird’s digestive tract have been more invasive, while analyzing the stomach contents of a dead bird depends on a biased sample set (bird carcasses that have washed up on shore, for example).
Preening oil is produced by the uropygial gland at the base of a bird’s tail, and is vital to maintaining waterproofed feathers. Petroleum destroys such waterproofing, which impedes a bird’s ability to regulate body temperature. Scientists at CSIRO’s Oceans and Atmosphere Flagship in Australia report that by collecting oil form the gland with a swab, they can measure levels of phthalates — chemical compounds that make plastic more durable and flexible. The amount of phthalates in preening oil correlated with the amount of plastic swallowed by the animals studied.
The research is published in the journal Methods in Ecology and Evolution.