Oil Spill Effects on Wildlife: It Only Takes a Drop of Oil

Harm to wildlife, predominantly waterbirds, is where you’ll see the most obvious oil spill effects. Many birds that encounter oil do not survive. Oiled wildlife that do survive, face both short-term and long-term health consequences. Learn how oil affects waterbirds and other wildlife and how wildlife rehabilitators work to save them.

To Understand Oil Spill Effects on Birds, You Must First Understand Waterproofing

Understanding the oil spill effects on birds starts with understanding waterproofing. The greatest harm to birds, in particular waterbirds, is that a single drop of oil destroys the bird’s waterproofing.

It’s a common misconception, amongst amateur and professional biologists, that the oil gland provides the waterproofing a bird needs. This is not true. In fact, it’s the structure of

bird feather barbs barbules

Pull a feather apart and you can feel the pull of the barbs.

the feather that provides a bird its waterproofing. If you look at a feather under a microscope you’ll see that there are small barbs and barbules throughout the feather. Oil spill wildlife rehabilitation experts at International Bird Rescue report that, “These barbs and barbules hook together like Velcro to form a tight waterproof barrier. Each properly aligned feather overlaps another like the shingles on a roof to create an entire waterproof covering for the bird.”

Uropygial glands do several things for a bird’s feathers including keeping them soft and in good condition and protecting against fungi, bacteria, and parasites, reports Ornithology author Frank B. Gill. These preening gland oils are used by the bird to condition the feather, keeping it soft and flexible and easier to reconnect those barbs and barbules as needed. UC Davis’ Oiled Wildlife Care Network states that the preening oils, “do not directly aid in waterproofing.”

You may be surprised to learn that many birds do not have well developed, or any, uropygial glands, commonly known as preening glands. This includes the anhinga, a waterbird that hunts and captures its prey of fish under water, and yet its skin remains warm and 100 percent dry if the feathers are in top condition and properly aligned. The outer feathers will retain water due to a difference in feather structure allowing the bird to dive deeper. But the under layers of feathers and skin remain dry, despite the under developed preening gland.

Oil Effects on Waterproofing

oiled bird feathers

Oil mats and damages the structure of feathers. Wikimedia Commons: Mila Zinkova

When a bird’s feathers come in contact with even a drop of oil, the oil essentially creates a hole in the waterproofing of the feathers. Like a hole in the roof, water can now flood under the feathers and air flows out. The bird looses its layer of warm air and quickly becomes hypothermic. Heavy amounts of oil, lack of buoyancy, and being just too cold prevents the bird from being able to hunt for food.

Oil Effects on Organ Systems

Contact with the oil can cause chemical burns to the skin, internal digestive problems, and respiratory problems. Studies have shown oil can also damage the liver, kidneys, and other internal organs.

Rehabilitation Challenges of Pelagic Birds

In addition to the harm the oil causes to waterproofing and organ systems, pelagic birds lucky enough to find their way to an oil spill wildlife rehabilitation center face additional health concerns from just being on land.  Pelagic species of birds, such as grebes and loons, live their entire life on the water or in the soft marshlands surrounding water. They are not designed to even walk on land and do not survive well on land. Because of their unique anatomy, they can easily develop lesions on their feet and keels. These can be life threatening and can occur within a few days. They also do not have a natural immunity to land borne fungi spores that land animals do have immunity to and fungal lung infections become a concern.

oil spill effectsPopulation Declines

Oil spill research indicates that for every bird collected, dead or alive, another 10 to 100 birds are never accounted for. During the Deepwater Horizon Gulf Oil Spill, the U.S. Fish and Wildlife Service reported in September 2010 that 4,676 birds were collected from the spill area, of which 1,042 were alive and sent to rehabilitation centers. The National Wildlife Federation put that figure at more than 8,000 animals (birds, sea turtles, and mammals) six months after the spill. On the conservative end, that may mean another 46,000 birds and other wildlife were affected by this one oil spill.

For large populations of species, recovery from a spill is possible. But for small populations, the oil spill has the potential wipe out a species and change the ecology of the region.

Long Term Oil Spill Effects on Wildlife

Long term research has shown that oiled birds rehabilitated and released can have decrease breeding and hatching rates for several years following surviving an oil spill. However, research has also shown that these oil spill effects are not necessarily permanent conditions and many oiled birds rehabilitated and released do have normal breeding patterns and normal lifespans. The species, type of oil, and severity of the oiling can all impact these long term results.

Other Animals

Of course birds are not the only animals affected by oil spills, just the most numerous. Any animal that lives in or near water can be harmed by coming in contact with spilled oil, and the effects are much the same. Other species affected by oil spills have included turtles, sea lions, seals, dolphins, fish, and crustaceans.

Help for Oil Spill Affected Wildlife

Experts working in oiled wildlife rehabilitation become the salvation for animals caught in an oil spill. Not only are they able to restore a bird’s waterproofing, bring them back to health, and release many oiled birds and other animals back into the wild, their work may have saved entire populations of birds. For example, in 1999 about 60%  (about 45 birds) of the Oregon population of the Western snowy plover, a threatened species, were oiled. Of those 45, 32 birds were captured, rehabilitated, and released. The population of Oregon’s snowy plover population grew from 73 in 1999 to 181 in 2007. Without oil spill rehabilitation, it’s unknown if the 25 non-oiled birds would have sustained the population.

When an oil spill occurs, it’s easy to blame and villainize the company responsible for that spill. But oil is something that currently developed nations cannot survive without. Oil creates energy to power our cars and heat and light our homes. Petroleum also makes polyester, plastics, carpets, and candles. If you are sitting at your computer in a house with carpet, light, and heat, then you are at this moment using and benefiting in many ways from oil. Improved laws and regulations can help prevent spills, but as long as there’s dependence on petroleum for energy and products, mistakes will happen that lead to oil spills. You can help mitigate the oil spill effects on wildlife today by becoming a wildlife rehabilitation volunteer.


  1. The Distribution and Reproductive Success of the Western Snowy Plover Along the Oregon Coast 2007.
  2. Ornithology by Frank B. Gill, 1995
  3. International Bird Rescue: How Oil Affects Birds
  4. UC Davis Oiled Wildlife Care Network: Impacts of Oil on Seabirds

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