Yarn Registry BLOG: A Landfill is an Ecosystem Unto Itself, part IV
- Published: December 2, 2016
Loafing, foraging, socially interacting: Birds
Part 4 of a series investigating the many layers of life in the average landfill. This week’s entry discusses the birds that flock to landfills, and how this unusual environ has affected their behavior and health. Next week: Mammals!
Kestrels, sandpipers, killdeer, and doves flutter and glide majestically over top the acres of landfill — those are some of the bird species that call the Rumpke grasslands home. Birdsong mixes with the rattle and hum of machinery to create a cyborg symphony that represents the in/organic mix that is the landfill itself. The small rodents and reptiles that live in the garbage grasslands make for a good meal, and the landfill itself provides abundant resources for creatures to consume. Kestrels, the continent’s smallest falcon, can see ultraviolet light, which means it can see things like the urine trails left by small mammals, which live in abundance on a landfill’s grounds. Kestrels hide their prey in small cavities like grass clumps, bushes, or crevices in man-made structures, which likewise exist in abundance on landfill properties.
Birds flock to the landfill to eat and socialize with their brethren. Their acute senses and fearlessness allow them to eat as the humans and machines work, excavating waste not buried deep enough. A landfill in Virginia reported that it attracted 25,000 birds per day, and its daily take was only 900 tons of garbage (vs. Rumpke’s 6,000). “Loafing or social interacting” among herring gulls nesting near landfills near the Great Lakes was found to be the most prevalent activity in areas other than exposed refuse, though “aggression” was common too. Foraging was (understandably) the most frequent activity in areas with open garbage.
Landfills can provide a stable and food source for birds. As we’ve seen, organic waste makes up approximately half of the midden’s contents. One study found that a landfill in Vancouver might have contributed to the survival of bald eagle populations over winter (or at least sustaining more eagles than could normally be expected) due to the food available in the landfill. The study noted that the overall number of eagles peaked during rough weather because the landfill is protected from the wind, is slightly warmer thanks to decomposing garbage, and has fairly minimal human activity.
But the victuals in a landfill are significantly less nutritious than the food that a bird might naturally consume. Food from a landfill is literally junk food. The trade-off is its convenience, but this also means any other creature feasting on a landfill has to consume more to get the nutrition they require. This is especially true for birds, whose energy expenditures require a relatively high food consumption per unit weight. Needing to eat more means more time in the landfill, which means more exposure to predators and dangers like machinery. And more activity overall means a greater expenditure of energy, which necessitates more nutritious food. Foraging at landfills can also significantly affect birds’ health and reproduction, considering the likelihood that birds will consume non-food items or items and contamination by toxins. Sadly, young birds have often been found starved to death in landfills, with stomachs full of plastic and other inedible/indigestible items. Eagles have died after eating euthanized animals that were improperly wrapped at landfills on Vancouver Island. Dozens of Glaucous-winged gulls died after ingesting chocolate at another landfill in Vancouver.
To get a more detailed understanding of the role the landfill played in the dietary habits of the birds that flocked there, researchers collected food remains and food pellets from colonies of herring gulls. They also took samples of the stomach contents (boli) of the gull chicks. “If a chick did not regurgitate upon capture,” the study says, “we inserted a finger into its proventriculus and removed the contents.” The authors found that fish was the most common food during incubation and chick-rearing, likely because it is significantly more nutritious. Adult herring gulls that specialized on garbage fledged fewer chicks than did adults that specialized on other foods. After fledging, the gulls were shown to eat more garbage, when their bodies are better able to maximize nutrients.
Eagles are primarily avivores, and the researchers who conducted another study expected that eagles would feed primarily on the gulls at the landfill. Ultimately, almost all of what the eagles ate was household food waste, and in particular red meat waste and bones. “Although some meat was identifiable, most was identifiable and clearly putrid or decomposing,” researchers wrote. Garbage made up 6.6 percent of the eagles diet, including paper towels and plastic bags. Overall, landfill refuse accounted for only around ten percent of the energy intake of the eagles that frequented the landfill. Younger eagles were apparently the refuse specialists, likely because younger eagles are less efficient hunters than adults. Eagles were also able to snatch food from other unwitting birds feeding at the site.
Despite their questionable offerings, landfills are so convenient to feeding that they’ve disrupted migratory patterns. Researchers observed white storks staying in landfills year-round in Portugal and Spain instead of their annual winter migration to Africa. The storks began staying in dumps the 1980s, in an area where they had never been seen before. The number of storks wintering in the landfills increased from around 1,200 to 14,000 between 1995 and 2015. Over several years, Birds were fitted with GPS devices, which revealed that the storks were eating, breeding, and permanently living in the landfill, as well as guarding “desirable locations” in the landfills. “We think these landfill sites facilitated the storks staying in their breeding sites all year because they now have a fantastic, reliable food source all year round,” said one researcher, though the impact of dwindling amounts of birds on the ecosystems they abandoned is yet to be seen.
Overall, bird populations are more closely controlled than those of other creatures living on the landfill. Birds at landfills are considered especially irritating to landfill managers and the surrounding homes and businesses, as well as a cause of concern to nearby airports. “The county abandoned recreational ballfields at the landfill to avoid the excessive bird droppings, and paint on nearby vehicles and buildings were damaged by the steady rain of fecal material,” reported one study. As such, one of a landfill’s pest-control directives is to reduce the amount of birds on site. Rumpke contracts with a US Department of Agriculture wildlife specialist that focuses on monitoring the bird population.
 Contents were separated into categories – fish, garbage, insects, plant food – and counted. Garbage comprised roughly 11% of the boli’s contents, 17% of the food remains found near nests, and less than one percent of the content of the food pellets.