How much plastic can an albatross chick swallow?
The answer: An absolutely staggering amount.
The volume of plastic that can be found in the carcasses of chicks would choke the proverbial horse. And the size of the items the chicks have apparently swallowed is also dismaying: A five-inch long, inch-and-a-half wide cigar-shaped float from a fish net; a piece of black plastic tubing nine inches long and half an inch wide; a five-inch-long model of a dinosaur; fishing lures; light sticks; cigarette lighters; toothbrushes; lotion bottles; asthma medication inhalers; soy sauce containers; wheels from toy planes and cars and the toys themselves.
On display at the visitor center at the U.S. Fish and Wildlife Service’s Midway Atoll National Wildlife Refuge, the contents removed from the carcass of a single chick are mounded up into a pile that is a foot square. A study of plastics ingested by seabirds in the late 1980s reported that the largest single item researchers found in an albatross stomach was a plastic sheet having a volume of 200 cubic centimeters, or about 12 cubic inches.
Question Number Two: How much can an albatross chick swallow and still live?
This question has biologists at the U.S. Fish and Wildlife Service’s refuge at Midway Atoll scratching their heads. At a certain point in the chick’s development, the indigestible parts of meals fed to it by its parents can be regurgitated in a fist-sized bolus stained the dark purple-brown of squid ink. In an ideal world, the bolus consists almost entirely of squid beaks and the occasional nut or small pumice stone. After coughing up the bolus, biologists think, the chick is no longer in danger of starving to death as a result of its stomach being filled by plastic that displaces food it would otherwise receive from its parents. Even if starvation does not kill the chick, it may die of dehydration, since its only source of water is from the squid or flying fish eggs it receives from its parents. In other words, if the chick cannot feed, it risks dying of thirst. And even if it doesn’t die outright of thirst or starvation, any chick that is weakened by poor nutrition or dehydration will be far more vulnerable to potentially fatal diseases than a healthy, well-nourished chick.
Sharp edges on plastic fragments – such as the broken lid from a jar of Maxwell House instant coffee that I saw on a recent trip to Midway – can lacerate the bird’s throat and lining of the proventriculus, the part of the stomach before the gizzard where preliminary digestion occurs. This, too, can lead to death.
Other problems can arise from ingestion of plastics. While at sea, floating plastic debris may acquire a thin film of several of the toxic chemicals that exist at relatively low concentrations in the ocean water and atmosphere. These include polychlorinated biphenyls (PCBs), dioxins, and furans, which are increasingly turning up in the body fat of sea birds and other marine animals. Some of the known effects of these organochlorines include reproductive difficulties and, at high levels, deformities and death
Many of the plastic fragments the birds ingest have been melted, a process that creates dioxins and furans. This has led some scientists to think that the simple fact of ingesting plastic may itself increase the levels of these toxins in albatross.
Deadly Diet
There are two islands at Midway that visitors may tour: Sand Island, where visitor accommodations, offices, and the airstrip are located, and Eastern Island, where tours are more strictly limited to protect resident bird populations.
On Sand Island, maintenance crews pick up the carcasses of Laysan and Black-footed albatrosses and their chicks — about 200 a day, on average, during the months the chicks fledge (January to July). But on Eastern, birds that die are left where they fall, and the story these carcasses tell is sobering indeed.
On a recent tour of Eastern Island, I came upon two skulls of albatross, their bills interlocked as though they died while one of the birds – an adult — attempted to feed the other, its chick. (Chicks are fed when a parent regurgitates the contents of its stomach to the chick.) A pink toothbrush was clutched in the bill of one of the birds. The carcass of the chick had decomposed to the point its stomach contents were visible: at least three plastic cigarette lighters (blue, red, and gold); an asthma inhaler; several bottle caps; plastic tubes; wadded up netting and monofilament line; and assorted plastic fragments of uncertain origin. No one can say with scientific certainty that the chick died of starvation. But with a stomach this full of plastic, how could the chick possibly have survived?
Where does the plastic come from? Lettering on many of the cigarette lighters suggests they originated in Korea, China, or Japan. Yet refuge personnel are quick not to pin the blame on any one group or nationality. Much of the plastic is related to fishing gear and it’s easy to imagine that much of the remainder is also from Asian fishing vessels that ply the Northern Pacific – fishing crews tossing their empty lighters over the side of the boat, discarding bottle caps, unusable gear, et cetera.
Again, though, the evidence is confounding. How does one account for the toys, bottles, toothbrushes, clothes pins?
When plastic is discarded on land, it is swept up by rain and carried into rivers or washed into storm drains that empty eventually into the sea. Not all plastic products will float, but many do — essentially forever or until they are swallowed by a turtle or scooped up by a bird. In either case, the plastic may be ingested deliberately, having been mistaken for food, or incidentally, when the plastic is floating alongside the targeted fish or eggs. The presence of so much plastic from the Orient is explained, at least in part, by the prevailing Kuroshio ocean current, which tends to run from Japan eastward across the Northern Pacific.
In the 1980s, scientists attempted to understand how much plastic seabirds were ingesting. They found plastic in almost every Laysan and Black-footed albatross chick they examined. Every chick carcass they found and necropsied contained plastic. The scientists also studied plastic in other seabirds, including petrels, shearwaters, and tropicbirds. These species also ingested plastic, but in much smaller amounts.
Some scientists believe the amount of plastic ingested by albatross is growing, but the work done in 1986 and 1987 by researchers from the U.S. Fish and Wildlife Service suggests it may vary year to year. Fewer plastic items were found in albatross chicks in 1987 than in 1986, they noted. This could be the result of less plastic in the sea – or, at least, of less plastic in the specific waters where the albatross forage.
Overall, though, the level of plastic in the Northern Pacific Ocean is high compared to what is found elsewhere. In 1987, the mean density of plastic in Alsakan waters was 910 particles per square kilometer; in the South Atlantic it was 2,080 particles per square kilometer – but in the subtropical North Pacific, it was 96,100 particles per square kilometer.
Since then, the production of plastic products has increased rapidly. Global consumption of five of the most commonly used plastic resins stood at 95.6 million metric tons – 210 billion pounds — in 1996, according to the American Plastics Council. And if consumption has continued to grow at the rate of 6 percent a year – the rate seen between 1994 and 1996 – that means that by 1999, the world manufacture of plastic products amounted to nearly 114 million metric tons.
Double Jeopardy
Why are chicks so vulnerable to plastics?
Chicks cannot regurgitate the undigestible contents of their stomach until they are well along in the process of fledging. All through this time, which runs generally from late January-early February until late June-early July, the chicks are the repository of everything their parents pick up from the ocean: squid, flying fish eggs, toy airplane wheels, plastic sponges, and every other manner of floating detritus. At the same time that the adults are feeding their offspring, they are transferring to the youngsters their own load of plastic. This “intergenerational” transfer of plastic “reduces occurrence in the adult populations while increasing it in the chick populations,” according to the scientists who studied plastic ingestion in the 1980s.
Despite the plastic, about 75 percent of the Laysan albatross chicks that hatch at Midway in any given year survive and, after fledging, will go to sea. There they will remain for three to five years or even longer. After that, they will return to Midway and rejoin the other 800,000 or so birds of their species that nest on the atoll, home to more than two-thirds of the Laysan albatross’ global population. It may take juveniles two or three more years to select a mate (they bond for life) and to produce their first chick.
Will they live happily ever after? If they avoid plastic, avoid getting hooked by longline vessels, and stay clear of the planes at Midway, Laysan albatross won’t live forever, but they’ll still live a mighty long time: some birds banded in the 1960s are still flying today.
— Patricia Tummons
For Further Reading:
Louis Sileo, Paul R. Sievert, Michael D. Samuel and Stewart I. Fefer, “Prevalence and Characteristics of Plastic Ingested by Hawaiian Seabirds,” in R.S. Shomura and M.L. Godfrey, eds., Proceedings of the Second International Conference on Marine Debris, NOAA Technical Memo, NOAA-TM-NMFS-SWFSC-154, 1990.
Ted N. Pettit, Gilbert S. Grant, and G. Causey Whittow, “Ingestion of Plastics by Laysan Albatross,” Auk, Vol. 98 (October 1981).
Volume 11, Number 2 August 2000