Pollution's Impact: Counting Seabirds Affected By Human Negligence

Seabirds are extremely vulnerable to the effects of pollution, from oil spills to plastic waste. In the case of oil pollution, a single incident can affect a huge proportion of a breeding colony, and even a relatively small amount of oil can have long-term effects on breeding success and survival. Plastic pollution is also a significant threat, with over 56% of seabird species globally affected by plastic waste. It is estimated that one million seabirds die each year from ingesting plastic, and this problem is only getting worse.

Oil spills

Seabirds are particularly vulnerable to oil spills due to their frequent contact with the ocean's surface, where oil forms a film. When oiling occurs, the feathers of seabirds become matted and lose their waterproofing properties, leading to reduced buoyancy and increased difficulty in maintaining body temperature. This can result in hypothermia and, in severe cases, death. Ingesting oil while preening can also lead to serious health issues, including liver and kidney damage, digestive problems, and destruction of red blood cells (anaemia).

The toxic effects of oil spills can have both immediate and long-lasting consequences for seabird populations. Oil spills can contaminate the food sources of seabirds, leading to reduced food availability and displacement from their usual foraging habitats. This can result in malnutrition and increased energy expenditure, leaving the birds more susceptible to disease and reproductive issues. Oil spills occurring during mating and nesting seasons can have particularly severe impacts, as exposure to oil can hinder the birds' ability to reproduce.

The impact of oil spills on seabirds can also be felt by birds that live on land. For example, the seaside sparrows (Ammodramus maritimus) in the marshlands along the Gulf of Mexico were affected by the Deepwater Horizon oil spill, even though they do not typically venture out to sea. The oil that washed into the marshes coated the marshgrass, killing it and causing soil erosion. The long-term effects of this oil spill on the sparrow population are still being studied, but initial results suggest that sparrows nesting in previously oiled marshes had lower success rates in raising their young.

The polycyclic aromatic hydrocarbons (PAHs) present in oil are of particular concern. PAHs can cause endocrine disruption, leading to thyroid hormone suppression and compromising the ability of surviving birds to recover. The toxic effects of PAHs can impact the birds' metabolism, immune system, and reproductive capabilities. Unfortunately, survival rates for rehabilitated oiled birds remain low, even with significant resources invested in their care.

Plastic ingestion

Seabirds are highly vulnerable to the effects of pollution, and plastic ingestion is a significant issue. It is estimated that each year, hundreds of thousands of seabirds ingest plastic, with one million birds dying as a result. This problem has grown exponentially, with less than 5% of birds found with plastic in their stomachs in the 1960s, increasing to over 80% by the 1980s. It is projected that by 2050, 99% of seabird species will be ingesting plastic.

The Midway Atoll in the Hawaiian archipelago, home to the world's largest albatross colony, illustrates the devastating effects of plastic pollution. Despite its remote location, the atoll faces a severe plastic pollution problem, with an estimated 100 pounds of plastic washing up weekly. As a result, approximately one-third of albatross chicks die each year from ingesting plastic.

The issue of plastic ingestion is not limited to a single species. For example, in a study of Cory's shearwaters, 88.89% of the birds were found to have ingested plastic, with most of it coming from fishing gear. Similarly, in a study of Flesh-Footed Shearwater chicks, 90% were found to have plastic in their stomachs.

The impact of plastic ingestion on seabirds highlights the urgent need to address plastic pollution in our oceans and reduce the use of single-use plastics.

Plastic entanglement

Fishing gear is the primary cause of entanglement, entangling 83% of the 265 entangled bird species globally. The impact of plastic entanglement on birds is more obvious than that of plastic ingestion, as the effects are immediate and include impaired movement, making it difficult for birds to escape predators or find food.

While plastic entanglement is a serious issue for all seabirds, some species are more affected than others. A study by Laist (1997) found that 51 seabird species had been reported entangled in marine debris, including rockhopper penguins, geese, shorebirds, raptors, and passerines. Kühn et al. (2015) updated this list and found that 103 seabird species had been reported as entangled, concluding that all species of seabirds are at risk of entanglement.

The increase in plastic entanglement of seabirds is due to the increasing production and use of plastic worldwide. Plastic production has increased rapidly over the last 70 years, with more plastic produced in the first decade of this century than before 2000. Most waste plastic is either disposed of in landfills or released into the environment, and it persists for many years, dispersing far from its source areas. Rivers are a significant vector for plastic entering the oceans, and the northern Pacific's Great Pacific Garbage Patch, twice the size of Texas, is a prime example of the plastic pollution affecting seabirds.

While the exact number of seabirds affected by plastic entanglement is unknown, it is clear that it is a significant issue with devastating consequences for seabird populations.

Noise and light pollution

While it is difficult to find an exact figure for how many seabirds are affected by noise and light pollution, it is clear that these forms of pollution have a significant impact on seabird populations.

Noise Pollution

Noise pollution can increase birds' stress levels and reduce their sizes and life spans. It can also affect their ability to attract mates, establish nests, and listen for predators. Studies have shown that birds will avoid areas of excessive noise, including backyard feeders, indicating the widespread nature of this effect. Noise pollution can delay nesting and mate attraction, particularly in birds with songs at a lower frequency. Forest birds are more affected by noise pollution than birds in open environments.

One study found that constant noise could act as an "acoustic blanket", muffling the audio cues that birds rely on to detect predators, competitors, and their own species. This means that mother birds must choose between staying on guard at the nest and finding food for their young. Nestlings in noisy environments tend to have smaller body sizes and reduced feather development, which can diminish their odds of survival.

Light Pollution

Light pollution has been found to have a negative impact on many seabirds, including several globally threatened species. Many nocturnally active seabirds are sensitive to light pollution and can become easily disoriented by intense sources of artificial light. Coastal light pollution is a particular problem for fledgling petrels and shearwaters, which are lured to urban lighting as they attempt to make their first flights out to sea. Once grounded, they are often unable to become airborne again and frequently succumb to predation or starvation.

Artificial light sources have been found to attract at least 21 species of Procellariiformes (shearwaters, petrels, and albatross), as well as several other seabird groups, and have been found to have a detrimental effect on some globally threatened populations. Vulnerability to artificial lighting varies between different species and age classes and according to the influence of season, lunar phase, and weather conditions. In general, young birds are more likely to become disoriented by artificial light sources.

Chemical additives in plastic

For example, studies have shown that DEHP can cause weight gain and potential toxicity to the kidneys, liver, and cerebellum in birds. In addition, due to their hydrophobic nature and large surface area, microplastics can adsorb environmental contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). When these contaminated microplastics are ingested by seabirds, they can induce malnutrition, endocrine disruption, and reproductive issues.

The ingestion of plastic has also been linked to reduced survival and growth rates in seabird chicks. For instance, plastic ingestion has been observed to cause a minor delay in sexual maturity and a higher incidence of epididymal intra-epithelial cysts in male Japanese Quail chicks. Additionally, plastic ingestion can lead to reduced reproductive output, with studies showing that it can impact the reproductive success of Flesh-footed Shearwater and Japanese Quail.

Furthermore, the presence of plastic in the environment can affect seabirds' foraging behavior and distribution. Seabirds may mistake plastic debris for prey, leading to increased plastic ingestion. This is particularly true for surface-feeding seabirds, but diving seabirds, such as puffins, have also been found with plastic in their stomachs.

The impact of chemical additives in plastic on seabirds is a growing concern, and further research is needed to fully understand the extent of the problem and develop effective mitigation strategies.

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